chem lab final

Experiment 4:

- Be able to determine which reactant is the limiting reagent (by calculations and/or observation) and explain why. - Be able to calculate the theoretical and percent yield of the product. - Be able to mathematically explain how experimental errors would affect the end results. Calculations: See Exp. 3, and molessolution= Molarity x Liters and Molarity = moles / Liters

Experiment 11 - 14:

- Be able to identify cations from all of the Qualitative Analysis Groups in an unknown from data pages or experimental data using a flowchart from the known solution. - Be able to fill in chemical formulas on a data page and to write inferences and/or rationales on the identity of an unknown solution. - Be able to select a reagent to distinguish between cations (like quiz questions). Data Provided: A completed Known Flowchart and/or completed Known Data Page will be provided if needed for the question. Do not memorize flowcharts or data pages.

Experiment 15:

- Be able to use calculate specific heat, q and ∆Hrxn from experimental data. Understand the basic principles of calorimetry and how errors would affect results.. Calculations: qsoln = {specific heatsoln x masssoln x ∆Tsoln } and ∆Hrxn = qrxn / mole

A student takes 2.0 mL of a 0.20 M NaOH solution and then dilutes it with water to a final volume of 10.0 mL. -What is the Molarity of the diluted NaOH solution?

0.040 M

Ferris & Mona used the ORP sensor to titrate a ferrous ammonium sulfate solution, (NH4)2Fe(SO4)2 with KMnO4 titrant. They titrated a 12.50 mL aliquot of the Fe+2 solution with 0.0215 M MnO4- solution and determined that the equivalence point was at 10.8 mL. -What is the molarity of the Fe+2 solution? 5 Fe+2(aq) + MnO4-(aq) + 8 H+(aq) → 5 Fe+3(aq) + Mn+2(aq) + 4 H2O

0.0929 M

What is the Molarity of the Ba(OH)2 solution if a 12.50 mL aliquot of the Ba(OH)2 solution required 15.20 mL of a 0.108 M H2SO4 solution to reach the equivalence point? Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(l) **Can't do

0.128

a 20.94 g sample of metal is heated to 99.4 degrees Celsius in a hot water bath until thermal equilibrium is reached. The metal sample is quickly transferred to a 100.0 mL of water at 22.0 C containted in a calorimeter. The thermal equilibrium temperature of the metal sample plus water mixture is 24.6. What is the specific heat of the metal?

0.695 J/gC

Calculate the mole fraction of methanol (CH3OH) in a mixture that is 8.10 mL methanol and 8.13 g benzoic acid (C6H5COOH). The density of methanol is 0.792 g/mL and its molar mass is 32.04 g/mol. The molar mass of benzoic acid is 122.12 g/mol and is a nonvolatile compound.

0.75

NaOH is a strong base, that is, it completely dissociates in solution. So a 0.02 M NaOH solution really contains 0.02 M Na+ and 0.02 M OH- ions and no NaOH. -What is the expected pH of a 0.02 M NaOH solution?

12.30 pOH= -log(0.02) = 1.698 pH= 14-pOH pH = 14-1.698 = 12.3

What is the vapor pressure (in kPa) of CH3OH, methanol, over a solution which is composed of 8.00 mL of methanol and 8.05 g of C6H5COOH, benzoic acid, at 25ºC ? Pº methanol at 25ºC = 16.915 kPa Density of methanol is 0.792 g/mL Molar mass of benzoic acid is 122.12 g/mol

12.69 kPa **try to work out. How to do it w/o mass of methanol? Use molar ratio?

Using Raoult's Law calculate the vapor pressure of methanol over the mixture above at 25°C. The P°methanol at 25°C is 16.9151 kPa.

12.7 kPa can't work

A calibration plot of absorbance vs. concentration was obtained, with the slope of the best-fit straight line as 0.045 ppm -1. The absorbance of a dilute sports drink solution was measured in the spectrophotometer and recorded as 0.72. What is the concentration of Red 40 dye in this dilute sports drink solution?

16

A calibration plot of absorbance vs. concentration (ppm) was obtained with standard known Red 40 dye solutions. The slope of the best-fit straight line of the plot is 0.038 ppm- 1 The absorbance of the dilute unknown sports drink was 0.64 -What is the concentration of this dilute unknown sports drink ?

16.8 ppm absorbance = slope x concentration concentration = absorbance/slope concentration = 0.64/0.038 = 16.8

When 35 mL of 1.0 M HNO3 was mixed with 50 mL of 1.0 M NaOH in a coffee cup calorimeter, the temperature of the solution rose from 24.8°C to 31.7°C. -What is the qsolution in J and what is qrxn in J? - What is the ΔHrxn in kJ/mol of HNO3 neutralized? **MM of HNO3 = 63.01 g/mol

2451 -2451 **Dont know last one

An 5.00 mL aliquot of a 125 ppm stock Red 40 dye solution was diluted to a final volume of 25.0 mL with deionized water. What is the concentration of the dilute Red 40 dye solution (in ppm)?

25 ppm Concstock x volstock = concdilute x voldilute 125ppm x 5ml = concdilute x 25 ml concdilute = 125 x5 / 25 = 25 ppm

Given the data in the table on the back, determine the following: -What is the order of reaction for A? -What is the order of reaction for B? -What is the average value of the rate constant, k? -What is the rate constant expression or Rate Law?

A. 1 B. 2 C. 500 D. rate = (500 kpa sec ^-1 M^-3) [A][B]^2

For the Data Set on the back, determine the following: -What is the order of reaction with respect to E? -What is the order of reaction with respect to F? -What is the average value of the rate constant, k? -What is the rate constant expression or Rate Law?

A. 2 B. 3 C. 400 D. rate = k[E]^2[F]^3

When 4.51 g of CaCl2 dissolved in 50.00 mL of water in a coffee cup calorimeter, the temperature of the solution rose from 22.6°C to 25.8°C. Specific heat of the solution is equal to the specific heat of water = 4.18 J/gºC Density of the solution is equal to the density of water = 1.00 g/mL -What is qsolution? -What is qreaction ? -What is ΔHrxn in kJ/mol of CaCl2 ? **MM of CaCl2 = 110.98 g/mol

729 J -729 J -17.9 kJ/mol

A 146 mg sample of Red 40 dye was dissolved and diluted to a final volume of 2.00 L with deionized water. -What is the concentration of the Red 40 dye solution in ppm? parts per milliion (ppm) refers to 1 mg of solute in 1.0 L of solution; (mg/L)

73 ppm IDK how to do this**

Titrations are a type of stoichiometry calculation. In this experiment what is the mole ratio between citric acid and NaOH?

H3C6H5O7(aq) + 3NaOH(aq) --> Na3C6H5O7(aq) + 3H2O(l) 1:3

single displacement

AC + B → A + BC Cd(NO3)2(aq) + Zn(s) → Zn(NO3)2(aq) + Cd(s) One element (B) displaces an atom (A) in a compound (AC) to form a new compound (BC), while the displaced atom (A) is converted to its elemental form.

double displacement

AC + BD → AD + BC Cd(NO3)2(aq) + (NH4)2S(aq) → CdS(s) + 2 NH4NO3(aq) Zn(OH)2(s) + 2 HCl(aq) → ZnCl2(aq) + 2 H2O(ℓ)

Safety

Review the Safety Lecture and Good Lab Practices in the E-Book & Moodle. Know what various icons mean, what type of information is posted, and what PPE's are.

Experiment 10:

Review the concept of vapor pressure and be able to calculate Χsolvent (mole fraction) and Psolvent in Raoult's Law..

actual yield (experimental yield)

amount of product recovered in the experiment

Describe the mixtures as soluble, insoluble, miscible, or immiscible. - Al2O3 sinks to the bottom of a tall column filled with water. - Sand settles to the bottom of a pond. - Water and acetone mix completely. - Salt completely disappears when added to boiling water. - MgSO4 remains a solid when mixed with hexane (ℓ).

insoluble insoluble miscible soluble insoluble

In this experiment, you will be using and measuring various chemical species by a variety of units. Which units of measure is used for the vapor pressure of water? milliliters torr grams Kelvin

torr

whats a weak electrolyte

weak electrolyte is any substance that when dissolved in water partially dissociates into ions, so a few ions are present and it conducts electricity weakly

A set of known concentrations of Red 40 dye solution was used to make a calibration plot of absorbance vs. concentration (in ppm). The slope of the best-fit line was 0.067 ppm -1. A 5.0 mL aliquot of strawberry soda was diluted to a final volume of 100 mL with deionized water. The absorbance measurement of the diluted soda solution was recorded as 0.67. -What is the linear equation for this experiment? -What is the concentration of Red 40 dye in the diluted soda solution? -What is the concentration of Red 40 dye in the original strawberry soda?

y = 0.067x +b 10 200

If you weigh the Cu(C7H4SO3N)2(H2O)4·2 H2O crystals while they are still wet, will this affect your actual yield? If so, explain how.

yes, the weight of the water will be added to the weight of the product, increasing the actual yield

what is the first law of thermodynamics

The First Law of Thermodynamics states Energy is conserved. So the heat released by the system plus the heat gained by the surroundings must equal zero. Thus the heats of the system and surrounding are equal in magnitude, but opposite in sign

Adding mercury(ℓ) to water results in a solution consisting of two layers. -What describes the relationship between mercury and water?

immiscible

Will use of a lower Molarity value of ascorbic acid affect the calculated Molarity of DCIP? -Raises the value of Molarity of DCIP -Lowers the value of Molarity of DCIP -No effect

lowers the value

A coffee cup calorimeter contained 50.0 mL of a 1.33 M KOH solution at an initial temperature of 24.3 ºC. A student quickly add 35.0 mL of 1.42 M HNO3 to the calorimeter. The maximum temperature reached during the neutralization reaction was 29.1ºC. Determine the ΔHrxn for this neutralization reaction in kJ/mol of HNO3. *assume specific heat of solution is the same as specific heat of water = 4.18 J/gºC *assume density of both KOH and HNO3 are the same as water = 1.00 g/mL *if negative value, be sure to type in a minus sign. HINT: You will need to first find qsolution.

masssoln = (mL HNO3 x 1.00 g/mL) + (mL KOH x 1.00 g/mL) ΔT = Tfinal - T initial qsoln = specific heat × masssoln × ΔT qrxn = (-) qsoln mol HNO3 = M HNO3 x L HNO3 ΔHrxn = qrxn / mol HNO3 The correct answer is: -34.3 **IDK how to do this

What would happen if you mixed water, olive oil, and an ice cube in a beaker?

middle - olive oil bottom - water top - ice cube None would mix since they are immiscible with each other *The most dense layer goes to the bottom--least dense floats to the top

In this experiment, you will be using the gas constant, R. Which unit is NOT found in R? molarity Kelvin atmosphere liter

molarity

What is the oxidation number of Mn in MnO2 ?

+4

What is the oxidation number of Mn in MnO4− ?

+7

using the picture on the back: -What is the reaction order of D ? - What is the reaction order of E ?

- 1 - 1

LeChâtelier's principle also extends to equilibria involving gas phase reactions. Partial pressures can be treated as concentration. However, if the total pressure is increased, then the system shifts to the equilibrium side that contains fewer moles of gas. Predict the equilibrium shifts that will occur in the endothermic equilibrium reaction below in order to re-establish equilibrium. CH4(g) + H2O(g) ⇋ CO(g) + 3 H2(g) -Increasing the partial pressure of carbon monoxide gas. - Decreasing the overall total pressure of the equilibrium system.

- will shift the equilibrium towards the reactants - Will shift the equilibrium towards the products

Predict the initial rate (in kPa/sec) for Trial D using the data. Use pic on back

0.012

Using Raoult's Law, predict the vapor pressure of ethanol (CH3CH2OH) over a solution that is a mixture of 11.00 mL of ethanol and 4.00 mL of ethylene glycol (C2H4(OH)2) at 20°C. The density of ethanol at 20°C is 0.789 g/mL and P°ethanol at 20°C is 5.95 kPa. The density of ethylene glycol 20°C is 1.113 g/mL and it is a nonvolatile compound. **MM of ethanol is 46.07 **MM of ethylene glycol is 62.07

0.6226 **Did work for this but can't check if its right

What is the mole to mole ratio between Cu(C2H3O2)2·H2O and NaC7H4SO3N·H2O?

1 mol Cu(C2H3O2)2·H2O : 2 mol NaC7H4SO3N·H2O

Cooper, Zach and Nate did this experiment dissolving 3.80 g of Cu(C2H3O2)2·H2O and adding 8.60 g NaC7H4SO3N·H2O (assume present in excess). What is the theoretical yield of the product, Cu(C7H4SO3N)2(H2O)4·2 H2O(s)? **MM of Copper (ll) acetate monohydrate = 199.65 g/mol **MM of Sodium saccharinate monohydrate = 223.18 g/mol **MM of product = 535.59 g/mol

10.19

Acids that are classified as strong acids (HX), are strong electrolytes because they dissociate_______ in water to form H+ and X-.

100%

What is the pH of a 0.020 M NaOH solution?

12.30

A 5.00 mL aliquot of a 0.20 M HCl solution is diluted to a final volume of 25.00 mL. - What is the molarity of this first dilution solution? Then a second dilution was made by taking 2.00 mL of the first dilution and diluting it to 50.00 mL. - What is the molarity of this second dilution?

1st Dilution = 0.0400 M; 2nd Dilution = 1.60 x 10-3 M

A common error in titration is over-titrating. Which of the following statement(s) is/are TRUE for the citric acid titration? 1) Over-titrating means too much analyte was added to the reaction. 2) Since the volume of titrant is too large, multiplying by a large number in the calculation of citric acid makes the mass of citric acid too high. 3) Over-titrating in this reaction produces a dark pink (or peach) solution.

2 and 3

Which of the following statements are TRUE if the standardization titration (Part II) was over‑titrated? 1)The molarity of DCIP would be lowered since the volume of titrant is in the denominator of the calculation. 2) Too much DCIP was added in the titration, causing the Molarity of the ascorbic acid to be lowered. 3) With a lower molarity of DCIP, the amount of Vitamin C will also be lower even if the titrations in Part II were done correctly.

2 and 3

Zach and Nate calculated the theoretical yield as 6.57 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. They recovered 4.53 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. - What is the percent yield?

68.9

combination

A + B → AB 2 Mg(s) + O2(g) → 2 MgO(s) Two elements or species come together to form one compound. **Pay attention to states!

decomp

ABC→ AB + C CaCO3(s) → CaO(s) + CO2(g) One species decomposes into two or more chemical species, generally as a result of heating.

Experiment 16:

Be able to interpret and explain observations in terms of Le Chatelier's principle as it relates to an equilibrium system when adding (or removing) chemicals or heat.

Cu(s) does not react with 10% HCl. Compare the reactions of Zn + HCl, Cu + HCl, and Mg + HCl. - Which reacted the most vigorously? - Which metal is the strongest reducing agent? - Which metal is the weakest reducing agent?

Mg (s) reacted the most vigorously. Mg (s) is the strongest reducing agent and Cu (s) is the weakest reducing agent.

What kind of errors might lead to a having a percent yield greater than 100%?

Not drying the product completely before weighting, so including the mass of water with product, increasing actual yield, thereby increasing percent yield -Basically, anything that increases the actual yield

In the generic reaction below, experimental data indicate the reaction is second order in A, first order in B and rate constant is 3.5 x 10 -3 M -2sec -1. Which is the correct rate constant expression? A(aq) + 2 B(aq) → A2B(aq) Select one: - Rate = (3.5 x 10 -3 M -2sec -1) [A] [B]2 - Rate = (3.5 x 10 -3 M -2sec -1) [A] 2 [B] - 3.5 x 10 -3 M -2sec -1 = [A]^2 [B] - 3.5 x 10 -3 M -2sec -1 = [A] [B]^2

Rate = (3.5 x 10 -3 M -2sec -1) [A]^2 [B]

In the Copper Cycle experiment, the dissolution of copper solid by the hydrogen peroxide was labeled as a redox reaction. Cu (s) + H2O2 (aq) + 2H+ (aq) --> Cu 2+ (aq) + 2H2O (l) Find the species being reduced, species being oxidized, oxidizing agent, and the reducing agent. (Redox Reactions)

Reduced: H2O2 (aq) Oxidized: Cu (s) Oxidizing Agent: H2O2 (aq) Reducing Agent: Cu (s)

For each trial, you did duplicate runs. How do the values of the initial rate of reaction compare? What does this indicate about the reproducibility of your results?

The initial rates of reaction were precise. This fact indicates that the results are reproducible.

what is Raoults law

The vapor pressure of the solvent over the solution (P) is equal to the mole fraction of solvent (Xsolvent ) multiplied by the vapor pressure of the pure solvent (P°). Psolvent =Xsolvent P°pure solvent

It was assumed that the water (or solution) absorbed all of the heat lost by the system. Do you feel this assumption was valid? If some of the heat were lost to the coffee cup or air, how would this affect your calculation of qsystem?

This would affect q system by decreasing it because if heat was lost by the cup or air, it wouldn't be accounted for

In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) H2O

non

What is the conductivity classification for an unknown C that dissolves completely in water and but doesn't dissociate into ions?

nonelectrolyte

What color is expected for the product, [Ni(C2H8N2)3]Cl2, if NiCl2·6 H2O is the limiting reagent?

pink violet

For the error, indicate if the error will affect the mg of citric acid present per mL of juice, and if it does, will it raise or lower the value of the mg citiric acid/ mL of juice? -Not subtracting the initial buret volume (1.20 mL) from final buret volume (18.43 mL) - No effect - Raises the value of mg citric acid/mL juice Correct - Lowers the value of mg citric acid/mL juice

raises the value

According to the solubility rules for common ionic compounds, all ionic compounds containing Na+ are soluble and dissociate 100%. -What electrolyte classification do you predict for Na+ compounds? -How does this compare to your experimental data with NaCl?

strong electrolyte strong electrolyte

theoretical yield

the amount of product that could be produced from the limiting reagent if the reaction were 100% efficient. This amount is calculated from the limiting reagent of reactant

percent yield

the ratio of the actual yield to the theoretical yield.

Predict the conductivity of NH2CH2CH2NH2, a weak base.

weak electrolyte

-What will you observe after the reaction is complete if NiCl2·6 H2O is present in excess? -What will you observe after the reaction is complete if C2H8N2 is present in excess?

filtrate is dark blue and blue violet filtrate is pink to lavender

In a certain reaction, a solid chemical dissolved in water. The temperature of the water sample dropped from 27.3 °C to 22.4 °C. From this description of the experiment, select the correct words to fill the blanks. This is a click and drag question, if your computer is not allowing the drag feature, then type in the answer EXACTLY as it is written in the box. The water is defined as the ______ The system _______ heat. qsystem has a ________ value. The reaction is an ______ reaction.

surroundings gained positive endothermic

When steel wool (Fe(s)—a gray solid) is heated in the presence of oxygen (O2(g)—colorless gas), a red-brown solid forms (iron(III) oxide). - Write the balanced equation for this reaction. Identify the species being reduced, species being oxidized, oxidizing agent, and the reducing agent.

- 4Fe (s) + 3O2 (g) --> 2Fe2O3 (s) - Oxidized: Fe (s) - Reduced: O2 (g) - Oxidizing Agent: O2 (g) - Reducing Agent: Fe (s)

Experiment 19:

- Be able to add two half reactions to obtain an overall redox reaction. - Be able to find the equivalent point volume from a redox titration graph and calculate the molarity of an unknown solution. Calculations: See Exp. 7 calculations

Experiment 17:

- Be able to calculate pH and to rank solutions by increasing or decreasing acidity (or basicity). Know buffer and buffer capacity terms and apply to experimental observations. - Be able to calculate the pH of a buffer solution. Calculations: pH = - log[H3O+] or pH = - log[H+] ; pH of buffer from weak acid equilibrium problem

Experiment 6:

- Be able to calculate the Molarity in a standardization titration.. - Be able to determine how many mg of Vitamin C is present in a sample and how many mL of juice is needed to meet the DRI of Vitamin C from similar data. - Be able to mathematically explain how experimental errors affect the various calculations. Calculations: Same as Exp. 5 and mganalyte / mLjuice

Experiment 5:

- Be able to calculate the molarity or mass of the analyte in a sample from known concentration. - Be able to mathematically explain how experimental errors affect the end results. Calculations: Use stoichiometric ratio to find moles of analyte; also find masssolid

Experiment 8

- Be able to calculate volume of O2 that will be generated from similar experimental data. - Be able to calculate % composition (by mass) of H2O2 from volume of O2 (g. - Be able to mathematically explain how experimental errors in calculations may affect the overall results. Calculations: PT = PO2 + PH2O and PV = nRT to use to calculate moles of moles, then use stoichiometric ratio to find moles of solution. Pay careful attention to moles of solution vs moles of gas.

Experiment 7:

- Be able to classify compounds based on their conductivity and/or ionization. - Be able to find the equivalent point volume from a conductimetric titration graph. - Be able to determine the molarity of an unknown solution from titration data. - Be able to describe each portion of the titration graph as it relates to the components/substances that are in solution. Calculations: - Mtitrant x equiv. pt. vol.titrant x (molanalyte/ moltitrant) = molesanalyte - Manalyte = molesanalyte / Lanalyte

Experiment 18: **Definitely go over problem on hayden Mcneil for this section

- Be able to determine the rate of reaction, individual orders of reaction, rate constant, and the rate constant expression (Rate Law) from experimental data or word problem. Calculations: - Mconc x Vconc = Mdilute x Vtotal - Rate = k [A]m[B]n - order = log Rate trial A/Rate trial B divided by log Conc. trial A/ Conc. trial B

Experiment 1:

-Know the terms and definitions of solubility, density, miscibility, and the difference between physical and chemical properties. -Be able to determine the densities and layering information of substances from data and/or an experimental description. -Calculations: Density (g/mL) = mass (g) / volume (mL)

Consider the exothermic equilibrium system below. The [CuCl4]-2(aq) ion is light green while the [CuBr4]2(aq) ion is dark brown. Originally the equilibrium below was a dark green. [CuCl4]-2(aq) + 4 Br-(aq) ⇋ [CuBr4]-2(aq) + 4 Cl-(aq) Predict the color of the solution after the system has re-established equilibrium. -Adding a small amount of white NaBr(s). -Adding a few drops of Ag+(aq) solution (Ag+ reacts with Cl- ions)

- Brown solution - Brown solution

Match the appropriate response to the following questions. What should you do if a . . . - chemical gets into your eye? - chemical is spilled on your hand? - person's hair or clothing catch fire? - chemical is splashed on your leg?

- Flush with eye wash solution for 15 minutes - Rinse with running water for 15 minutes - Wrap with a fire blanket and then stop, drop, and roll - Remove affected clothing and rinse with running water for 15 minutes

In a different rates of reaction experiment, the reaction being monitored was a redox reaction. S2O8-2(aq) + 2 I-(aq) → 2 SO4-2(aq) + I2(aq) Find the species being reduced, species being oxidized, oxidizing agent, and the reducing agent.

- I- is oxidized, reducing agent - S2O4 2-: reduced; oxidizing agent

In a different rates of reaction experiment, the fast reaction was a redox reaction. 2S2O3-2(aq) + I2(aq)→ S4O6-2(aq) + 2 I-(aq) Find the species being reduced, species being oxidized, oxidizing agent, and the reducing agent.

- I2: reduced; oxidizing agent - S2O3 2-: oxidized; reducing agent

Experiment 20:

- Know how to assign oxidation numbers. - Be able to determine which chemical species is the oxidized species, the reduced species, the oxidizing agent and reducing agent based on the observations or sample data.

In the redox reaction below, identify and match each reactant to their function. 3 CH3CH2OH (aq) + 2 Cr2O7−2 (aq) + 16 H+(aq) → 3 CH3CO2H (aq) + 2 Cr+3(aq) + 11 H2O(aq) -Cr2O7−2 (aq) -CH3CH2OH (aq)

- Species being reduced - Species being oxidized

Select the correct definition or example of the following terms: - Buffering capacity - Acidic buffer - Brønsted-Lowry base

- The amount of acid or base that can be added before the pH changes by 1 pH unit - A mixture of a weak acid and the salt of its conjugate base - Any substance that receives a proton

Define: - rate constant expression -reaction order -rate constant -initial rate of reaction.

- The mathematical expression of showing how the rate depends on the reactants in the rate-determining step. Rate = k [X]^m [Y]^n - The rate constant expression has a generalized expression shown above, where m and n are the reaction orders. - The rate constant expression has a generalized expression shown above, where k is the rate constant - The slope (Δpressure/Δtime) during the initial time segment

In the example equilibrium system, a drop of methyl orange indicator was added. For this indicator, the solution will be red in high concentrations of H3O+, and the solution will turn yellow in low concentrations of H3O+. - Initially the equilibrium solution was orange. What color is expected after the addition of the NaC2H3O2? Explain your reasoning. HC2H3O2(aq) + H2O(ℓ) ⇋ C2H3O2-(aq) + H3O+(aq) - Initially, the equilibrium solution was orange. What color is expected after the addition of a strong acid which donates H3O+ ions? Explain your reasoning. - Initially the equilibrium solution was orange. After heating the solution it changed to yellow-orange. Which way did the system shift? Explain your answer. - Initially the equilibrium solution was orange. Based on c., which color is expected if the mixture was placed in an ice bath? Explain your answer.

- The solution will be yellow because CH3COONa is a stronger base than acid, lowering the amount of H3O+ in solution. -The solution will be red because an acid was added to solution, which increases the amount of H3O+ in solution. - By heating the solution, equilibrium gives yellow-orange color which indicates the concentration of H3O ions decreases. Equilibrium will shift toward the reactants because the solution turned yellow, indicating a shift toward the reactants. - The concentration of H3O ions increases which gives the red orange color which is the opposite of C. The solution will be a red-orange color because equilibrium will shift toward the products.

Define: -limiting reagent -excess reagent

- The substance that is totally consumed in the reaction--limits how much products can be made -the reactant in a chemical reaction with a greater amount than necessary to react completely with the limiting reactant. It is the reactant(s) that remain after a chemical reaction has reached equilibrium.

LeChâtelier's principle also extends to equilibria involving gas phase reactions. Partial pressures can be treated as concentration. However, if the total pressure is increased, then the system shifts to the equilibrium side that contains fewer moles of gas. Predict the equilibrium shifts that will occur in the endothermic equilibrium reaction below in order to re-establish equilibrium. CH4(g) + H2O(g) ⇋ CO(g) + 3 H2(g) - Increasing the partial pressure of steam. - Increasing the overall total pressure of the equilibrium system.

- Will shift the equilibrium towards the products - will shift the equilibrium towards the reactants

Definitions - Irritant

- can cause itching, dryness, or sensitivity on skin or eyes

Definitions - Lachrymator

- causes eyes to produce tears

Definitions - Oxidizing agent

- causes other chemicals to be oxidized, reactive

Definitions - Corrosive

- irreversibly destroys living tissue when in contact with the skin or eyes

Definitions - Carcinogen

- is suspected or proven to cause cancer

Definitions: - Toxic

- may cause bodily harm through ingestion, inhalation, or skin absorption

Classify each of the following as either a physical or chemical property. - melting point - ability to dissolve metals - ability to react with oxygen - boiling point - color of liquid - ability to dissolve in water

- melting point is physical - ability to dissolve metals is chemical - ability to react with oxygen is chemical - boiling point is physical - color of liquid is physical - ability to dissolve in water is chemical

From the description of the reaction below, balance the equation and also select the classification of the reaction. When green FeO(s) is heated in the presence of O2(g), it forms a rust-brown solid, Fe2O3(s). _____ FeO(s) + ____O2(g) → ______Fe2O3(s)

- reaction is combination - Coefficients; 4,1,2

Match each item to its proper disposal method. - Used filter paper - Reaction mixture - Cracked or chipped beaker - Excess chemical

- trash can - Appropriate waste container - Broken glass box - appropriate waste container

A reaction mixture was formed by adding 50 mL of water, 10 mL of 0.88 M H2O2, and 10 mL of 0.5 M KI. -What is the molarity of the H2O2 in the solution? -What is the molarity of the KI in the solution?

-0.125 M - 0.0714 M

Consider an experiment where 7.50 mL of an unknown H2O2(aq) solution reacted with the yeast at 22.3°C to produce 82.34 mL of gas. The barometric pressure was 764.8 torr. The vapor pressure of H2O is 19.8 torr at that temperature. -What is the partial pressure of O2 (in atm) in the collected gas? -How many moles of O2 were produced by the reaction? -How many moles of H2O2 reacted to produce this amount of O2 ? -What is the Molarity of the H2O2 solution?

-0.9803 atm O2 -0.003329 mol O2 -0.006658 mol H2O2 -0.888M H2O2

Select all the statements that are true concerning pH and buffers. - As an acidic solution is diluted the pH decreases. -As a basic solution is diluted the pH increases. -The greater the concentrations of the buffer components, the greater its buffering capacity. -A buffer works when either acids or bases are added.

-A buffer works when either acids or bases are added. -The greater the concentrations of the buffer components, the greater its buffering capacity.

Select the step(s) that will compose a rationale for the cation Zn+2 being present in an unknown. Select one or more: -A precipitate formed when 6 M NaOH was added to the unknown solution in step 3-A. -A blood red solution formed when KSCN was added in step 3-D. -A pale yellow (tan) precipitate formed in step 3-H. -A purple-grape supernate over excess NaBiO3 formed in 3-G. -The colorless decantate was isolated in step 3-H when BaCl2 was added. -A grey-white solid formed in step 3-J.

-A grey-white solid formed in step 3-J. -The colorless decantate was isolated in step 3-H when BaCl2 was added.

Select the steps that will compose a rationale for the cation Ni+2 being absent in an unknown. Select one: -A red-pink solid did not form after the addition of H2DMG in step 3-F. -The lack of a green decanate after the addition of excess NaOH in step 3-A. -A blood red solution did not form when KSCN was added in step 3-D. -The lack of a yellow solution after the addition of H2O2 in step 3-B. -The lack of a purple-grape supernate over excess NaBiO3 in 3-G. -After the BaCl2 was added in step 3-H, a colorless solution with no solid was present. -The lack of a grey-white solid forming in step 3-J.

-A red-pink solid did not form after the addition of H2DMG in step 3-F. Correct

Experiment 9:

-Be able to use the equation of the line (from graph) to determine the dilute concentration of an analyte in an unknown. -Be able to determine the amount of analyte in an original unknown sample. - Be able to discuss the results of this experiment. - Be able to mathematically explain how experimental errors affect the various calculations. Calculations: Concstock x Volstock = Concdilute x Voldilute (Dilution equation) and Beer's Law: Absorbance = slope x concentration

What should you do if you spill a chemical on your lab bench? -Wipe it up with your towel. -Leave it for the janitor to clean. -Leave it along, it will evaporate -Clean it up using the spill kit in your lab

-Clean it up using the spill kit in your lab.

For the following error, select the answer that correctly describes how it will affect the value of the final temperature of the water/solution in the calorimeter: Stopped the recording of the temperature too soon, the maximum temperature had not yet been reached. -Decreases the value of final Temperature -Increases the value of final Temperature -No affect

-Decreases the value of final Temperature

Experiment 2:

-Identify the reaction type as one of 5 general types for a generic reaction and/or a chemical reaction. -Be able to classify and write a balanced molecular chemical equation from a written reaction description, including the correct phases.

-Immiscible -Density

-If two liquids do not mix completely, they will form layers -A substance's density is its mass to volume ratio (mass/volume). The layer with the lesser density will float or rise to the top of the denser layer.

Experiment 3:

-Know the difference between actual (or experimental), theoretical and percent yield. -Be able to calculate theoretical yield and percent yield of Cu(II) saccharinate, or some other known. A balanced chemical equation will be provided. -Be able to mathematically explain how experimental errors would affect the actual yield and percent yield. Calculations: - molessolid = Mass /Molar Mass -Mass = moles x Molar Mass - Convert from moles of A to moles of B using stoichiometric ratio from balanced rxn - Percent yield = (actual yield / theoretical yield) 100 %

Nick and Kel reacted 3.25 g of NiCl2· 6 H2O with 9.50 mL of 4.00 M C2H8N2. They recovered 3.43 g of product, [Ni(C2H8N2)3] Cl2. At the end, the filtrate was a dark blue solution. The litmus test on the filtrate solution left the red litmus paper unchanged in color. NiCl2· 6 H2O + 3 C2H8N2 → [Ni(C2H8N2)3]Cl2(s) + 6 H2O Molar Mass of NiCl2· 6 H2O is 237.69 g/mol Molarity of C2H8N2 is 4.00 M Molar Mass of product, [Ni(C2H8N2)3]Cl2(s) is 309.90 g/mol Based on the experiment described, select the correct answers for the questions below. -The chemical, C2H8N2, is the ... -The actual or experimental yield is ... -The chemical, NiCl2· 6 H2O, is the ... -The theoretical yield is ...

-Limiting reagent - 3.43 g - chemical present in excess - 3.93 g

Consider the equilibrium reaction below. At high concentrations of HA the solution will be blue; but at low concentrations of HA the solution will be red. Initially the equilibrium mixture below is purple (combination of red & blue). What color is expected after adding some colorless OH-(aq) to the equilibrium solution? A-(aq) + H2O(ℓ) ⇋ HA(aq) + OH-(aq) -Colorless -Purple -Blue -Red

-Red

Select all that apply to an exothermic reaction. Select one or more: -Heat is a product. -Adding heat (hot water bath) will cause the equilibrium to shift towards reactants. -Removing heat (cold water bath) will cause the equilibrium to shift toward products. -The reaction absorbs heat from the surroundings. -Heat is a reactant.

-Removing heat (cold water bath) will cause the equilibrium to shift toward products. -Heat is a product. -Adding heat (hot water bath) will cause the equilibrium to shift towards reactants.

-solubility -Miscibile

-The ability of a solid or gas to dissolve in a liquid -When two liquids mix completely with each other

Consider the benzoic acid dissociation reaction below which is at equilibrium. C6H5COOH (aq) + H2O(ℓ) ⇋ C6H5COO-aq) + H3O+(aq) If some strong base is added (the hydroxide ion which removes H3O+) is added to the system (stress), how will the system change in order to re-establish equilibrium? Select all that might apply. Select one or more: -The concentration of H3O+will stay the same. -The concentration of C6H5COO- will decrease. -The concentration of C6H5COO- will increase. -The concentration of C6H5COOH will decrease.

-The concentration of C6H5COOH will decrease. -The concentration of C6H5COO- will increase. because if you remove some product, some of the reactants will be used up to create more

If an error caused the mass of the solution to be larger, how does this affect the calculations? Select one: -The larger mass would have no affect since the specific heat of water is a constant. -The larger mass would result in a change in sign (from - to +) in the calculations. -The larger mass would result in a smaller ΔT. -The larger mass would result a larger qsolution.

-The larger mass would result in a larger qsolution.

- solvent - Solute

-The solution that does the dissolving -The substance being dissolved

Iggy, Lee & Brianne planned a new experiment based on two reactions involving Cu complexes they had previously observed in Exp. 11 & 12. [Cu(H2O)4]+2 (or simply as Cu+2) is a sky blue solution and [Cu(NH3)4]+2 is a dark royal blue solution. [Cu(H2O)4]+2(aq) + 4 NH3(aq) ⇋ [Cu(NH3)4]+2(aq) + 4 H2O(ℓ) -Make a hypothesis on what will occur in the equilibrium system (initially a medium blue solution) if additional ammonia is added. Then explain what will occur in terms of Le Châtelier's principle.

-The solution will become a darker blue solution. -The system must shift towards products in order to lower the concentrations of NH3. \

Piers & Aida added 1.25 mL aliquot of H2O2 to a beaker containing 5.0 mL of 6 M H2SO4 and 90 mL of water. The hydrogen peroxide solution required 20.80 mL of 0.0215 M MnO4- to reach the equivalence point using the ORP probe. 5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) → 5 O2(g) + 2 Mn+2(aq) + 8 H2O(ℓ) What is the molarity of the original H2O2 solution?

0.894 M(MnO4-) x L(MnO4-) x (5 mol H2O2/2 mol MnO4-) x (1/L H2O2) = M (H2O2) **Didn't work out

double displacement practice Ca(OH)2 + H3PO4 ---> 2) K2CO3 + BaCl2 ---> 3) Cd3(PO4)2 + (NH4)2S ---> 4) Co(OH)3 + HNO3 ---> 5) AgNO3 + KCl ---> 6) Na2CO3 + H2SO4 ---> 7) Al(OH)3 + HC2H3O2 ---> 8) Al2(SO4)3 + Ca3(PO4)2 ---> 9) Cr2(SO3)3 + H2SO4 ---> 10) AgC2H3O2 + K2CrO4 --->

1) Ca(OH)2 + H3PO4 ---> Ca3(PO4)2 + H2O 2) K2CO3 + BaCl2 ---> KCl + BaCO3 3) Cd3(PO4)2 + (NH4)2S ---> CdS + (NH4)3PO4 4) Co(OH)3 + HNO3 ---> Co(NO3)3 + H2O 5) AgNO3 + KCl ---> AgCl + KNO3 6) Na2CO3 + H2SO4 ---> Na2SO4 + CO2 + H2O 7) Al(OH)3 + HC2H3O2 ---> Al(C2H3O2)3 + H2O 8) Al2(SO4)3 + Ca3(PO4)2 ---> AlPO4 + CaSO4 9) Cr2(SO3)3 + H2SO4 ---> Cr2(SO4)3 + SO2 + H2O 10) AgC2H3O2 + K2CrO4 ---> Ag2CrO4 + KC2H3O2

An experimental method to estimate the density of a crystal is to compare it to a variety of known densities. Solution J (density = 1.9 g/mL), Solution K (density = 1.5 g/mL) and Solution L (density = 1.2 g/mL) are poured into a test tube. The liquids are immiscible with each other and solid M is insoluble in each. When a few crystals of M is added to the test tube, it sinks through solutions K and L, but floats on top of solution J. What is its approximate density?

1.2 g/mL - 1.9 g/mL

HCl is a strong acid, that is, it completely dissociates in solution. So a 0.02 M HCl solution really contains 0.02 M H+ and 0.02 M Cl- ions and no HCl. What is the expected pH of a 0.02 M HCl solution?

1.70 pH = - log[H3O+] or pH = - log[H+] pH = - log(0.02) = 1.70

What is the pH of a 1.8 x 10-2 M HCl solution?

1.74 pH = - log (H+) pH = - log (1.8 x 10-2) = 1.74

Cedrick & Astrid titrated a 20.00 mL aliquot of grapefruit juice with a 0.165 M NaOH solution to the end point. The initial buret reading was 1.72 mL and the final buret reading was 15.51 mL. H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(l) - what is the volume of the NaOH titrated -What is the mass of citric acid in the juice sample

13.79 mL 0.146 g

Ozzie used 5.20 mL of 2.21 M H2O2 and the partial pressure of O2 was 0.9341 atm and the temperature was 298.35 K. - What volume of O2(g) could he theoretically produce (in mL)? Enter your answer to 3 significant figures.

151

Cedrick & Astrid titrated a 10.00 mL aliquot of grapefruit juice with a 0.171 M NaOH solution to the end point. The initial buret reading was 1.31 mL and the final buret reading was 16.82 mL. They calculated that there was 0.1698 g of citric acid present in the juice sample.What is the amount mg of citric acid present per mL of juice?

169.8 mg/mL

When 5.0 g of CaCl2 was dissolved in 50 mL of water in a coffee cup calorimeter, the temperature of the solution rose from 22.3°C to 30.5°C. - What is the qsolution in J and what is qrxn in J? -What is the ΔHrxn in kJ/mol of CaCl2 dissolved?

1885 J -1885 J -41.8 kJ/mol

- How many electrons are transferred in the oxidation half-reaction? -How many electrons are transferred in the reduction half-reaction? - How many electrons are transferred in the overall reaction? Use pic on back

2, 3, 6 **IDK how to work

What is the density of a liquid that occupies a volume of 3.29 mL and weighs 2.98 g?

2.98/3.29 = 0.905 = 0.91 g/mL

When Cu(s) is heated in the presence of O2(g), the black solid, copper(II) oxide is formed. -Write the balanced redox reaction. -Find the species being reduced, species being oxidized, oxidizing agent, and the reducing agent.

2Cu (s) +O2 (g) --> 2CuO Reduced: O2 (g) Oxidized: Cu (s) Reducing Agent: Cu (s) Oxidizing Agent: O2

If some red-brown Cu(s) is heated with a Bunsen burner in the presence of O2(g), some black solid, copper(II) oxide, CuO(s), forms. Write the balanced equation for this reaction. Classify this reaction as one of the five general types.

2Cu(s)+O2(g)-->2CuO(s) combination reaction

- C12H7O2NCl2 is abbreviated as DCIP - Molar Mass of C6H8O6(s) is 176.14 g/mol C6H8O6(aq) + C12H7O2NCl2(aq) → C6H6O6(aq) + C12H9O2NCl2(aq) Ace, Corby & Astrid dissolved 0.0294 g of C6H8O6 in a 50.0 mL volumetric flask and filled it with deionized water to the mark. - What is the Molarity of this standard solution of C6H8O6 ? A 10.0 mL aliquot of the standard C6H8O6 above required 22.35 mL of DCIP to reach the endpoint. - What is the Molarity of the DCIP solution? A 15.00 mL aliquot of pear juice required 12.64 mL of the same DCIP solution (from above) to reach the end point. -How many mg of C6H8O6 are present in the aliquot?

3.34x10^-3 M 1.49 x 10^-3 M 3.32 mg **Molarity of C6H8O6 = (mass C6H8O6 / Molar Mass C6H8O6) / total volume in L **Molarity of DCIP = {M C6H8O6 (from above) x L C6H8O6 (aliquot) x (1 mol DCIP/1 mol C6H8O6) } / L of DCIP titrated **mg of C6H8O6 in juice = M DCIP (from above) x L of DCIP titrated x (1 mol C6H8O6/1 mol DCIP) x Molar Mass C6H8O6 x (1000 mg/1 g)

What is the pH of a buffer in which the concentration of benzoic acid, C6H5COOH, is 0.050 M and the concentration of sodium benzoate, NaC6H5COO, is 0.075 M ? Ka of C6H5COOH is 6.30 x 10-5

4.38 **didn't work out

C6H8O6(aq) + C12H7O2NCl2(aq) → C6H6O6(aq) + C12H9O2NCl2(aq) *C12H7O2NCl2 is abbreviated as DCIP *Molar Mass of C6H8O6(s) is 176.14 g/mol *Daily Recommended Intake (DRI) for adults: 90 mg of Vitamin C Askor & Bich found that it required 23.74 mL of 1.06 x 10-3 M DCIP solution to reach the endpoint when titrating a 20.00 mL aliquot of pear juice. -How many mg of ascorbic acid, C6H8O6, are present in the juice aliquot? -How many mL of this juice would Bich have to drink in order to meet the Daily Recommended Intake (DRI)?

4.43 406

Ethyl, Ann & Ami reacted 3.50 g of NiCl2·6 H2O with 12.00 mL of 4.00 M C2H8N2. They recovered 2.31 g of product, (Ni(C2H8N2)3)Cl2. - Theoretical yield of product is -percent yield is **MM of NiCl2·6 H2O is 237.69 g/mol **MM of C2H8N2 is 60 **MM of product is 309.8944 g/mol

4.56 50.6

What is the pH of a solution that has 0.060 M CH3COOH and 0.040M NaCH3COO present? Ka for acetic acid = 1.80 x 10-5

4.57 Buffer calculations for an acidic buffer, are simply a weak acid calculation where you have both the concentration of the weak acid and the salt of its conjugate base. In this reaction, the acetic acid is your weak acid and the sodium acetate is the salt of the conjugate base. CH3COOH + H2O ↔ CH3COO- + H3O+ Init. conc. init. conc. x Write the equilibrium constant expression for the weak acid dissociation of acetic acid. Then rearrange and solve for [H3O+], which is x. Next you will take that value of [H3O+] and find the pH. Ka = [CH3COO-] x [H3O+] / [CH3COOH] Ka x [CH3COOH] = [CH3COO-] x [H3O+] Ka x [CH3COOH] / [CH3COO-] = [H3O+] (1.80 x 10-5) x [acetic acid conc.] / [acetate ion conc.] = [H3O+] pH = -log [H3O+] The correct answer is: 4.57 **Didn't work out

Ozzie wanted to do another experiment using 20.0% (by mass) H2O2. What is the Molarity of this H2O2 solution ?

5.88 M *In the last step of the calculations we did in the lab, we converted Molarity of H2O2 into % by mass by the equation below. For this problem, we need to work it in the reverse. ***% (by mass) = Molarity H2O2 x Molar Mass × (1 / (Density) × (1 L/1000 mL) × 100% *we assumed the density of water and the hydrogen peroxide solution were both 1.0 g/mL since the solution is mostly water). However, this time start with the % and convert it to Molarity by rearranging the equation above. ***Molarity = % (by mass) / 100 x Density × (1/Molar mass) x (1000 mL/1L) Now substitution the definition of % (by mass) into the equation above. % (by mass) = (mass of H2O2/ mass of solution) ****Molarity = [(g of H2O2/g of soln) / 100)] x (1.0 g soln/mL soln) x ( 1 mol H2O2/ 34.01 g H2O2) × (1000 mL/1L) So the g of H2O2 cancels, and the mass of solution cancels, so the units left are mol of H2O2 per mL soln which is the definition of Molarity. **Can't do this one. Also, may be more complicated than what we are actually expected to do

How many mL of O2 would be produced by the reaction of 8.03 mL of 30.0% H2O2? The barometric pressure (Patm) was 752.4 torr and the temperature was 24.0°C. (Hint: Work this problem in reverse. Convert % H2O2 by mass to M of H2O2, then moles of H2O2, then moles of O2, then L of O2.)

89.8 mL of O₂ is it right though? Plus, I think this is too complicated to be tested on

A 6.0 mL aliquot of a 75 ppm Red 40 dye stock solution was diluted to a final volume of 50.0 mL with deionized water. What is the concentration of the new dilute Red 40 dye solution in ppm?

9

Cooper and Zach did this experiment dissolving 3.46 g of Cu(C2H3O2)2·H2O and adding 7.74 g NaC7H4SO3N·H2O. - They recovered 6.88 g of product. - In their calculations, they found that 9.28 g of product should be produced. Theoretical yield? Percent yield? Actual yield?

9.28 74.1 6.88

why does a buffer work

A buffer works because it has both a weak acid (HA) and its conjugate base (A-) present. The weak acid species reacts with any added base, and the weak (conjugate) base species reacts with any added acid. And the same is true for a weak base and its conjugate acid.

whats a non electrolyte

A nonelectrolyte is any substance that when dissolved in water stays as a molecule (doesn't form ions) and does not conduct electricity

Vida and Min dissolved 0.0521 g of C6H8O6 in a 100 mL volumetric flask with deionized water. A 10.0 mL aliquot of this standard C6H8O6 solution required 23.7 mL of DCIP to reach the end point. A 5.00 mL aliquot of orange juice required 14.4 mL of the same DCIP solution to reach the end point. -What is the molarity of the standard ascorbic acid solution? -What is the molarity of the DCIP solution? -How many mg of C6H8O6 are present in the juice sample? ** -How many mL of orange juice are needed to satisfy the adult DRI requirement for Vitamin C? ** **This is the most important version of this problem to study

A) 2.958 x10^-3 B)1.248 x10^-3 C) 3.145mg D) 142.23 mL

Rubbing alcohol is miscible with water and has a density of 0.785 g/mL. Olive oil is immiscible with rubbing alcohol and has a density of 0.92 g/mL. Water is immiscible with olive oil, miscible with rubbing alcohol, and has a density of 1.00 g/mL. -What will happen when water is added to a beaker, then the olive oil, and then rubbing alcohol? -What will happen if the layers are stirred and then allowed to settle?

A) Water would sink to the bottom, the olive oil will be in the middle, and the alcohol would float on top. (in order of densities) B) The rubbing alcohol with mix completely with the water and form the bottom layer, while the olive oil will float on top.

Equilibrium systems that include gas phases are also affected by Le Châtelier's principle. One difference is the effect of pressure. If the total pressure of the system is increased, then the system will shift toward the reaction side that has fewer moles of gas. Of course, if the total pressure of the system is decreased, then the system will shift toward the reaction side that has more moles of gas. For the equilibrium system below, state which way the system is expected to shift to offset the given changes. Then explain what happens to the partial pressure (or concentration) of SO2 during the shifts. 2 SO2(g) + O2(g) ⇋ 2 SO3(g) -Increase the partial pressure of O2 (increase the concentration of O2). -Increase the partial pressure of SO3 (increase the concentration of SO3). -Increase the overall total pressure of the system.

A) increasing P-O2 will favour products, i..e more production of SO3, therefore, SO2 partial pressure will decrease, since it will react to form more SO3 b)Increaseing the product, will shit to left, then reactants increases. Partial PRessure of SO2 will increase c)increasing PRessure in the system will favour the least mol production, that is, the right side, then SO2 partial pressure will decrease eventually

Two students titrated a 25.0 mL aliquot of pear juice with 0.17 M NaOH to the phenolphthalein end point. The initial buret reading was 0.73 mL and the final buret reading was 18.39 mL. a. What is the mass of citric acid in the juice sample? b. Calculate the mg of citric acid present per mL of juice.

A)0.577g B) 23.08 mg/ml

Nick, Ethyl, and Amy reacted 3.60 g of NiCl2·6 H2O with 8.50 mL of 4.0 M C2H8N2 and obtained 2.83 g of [Ni(en)3]Cl2. The filtrate was dark blue. Assume the density of the C2H8N2 is 0.950 g/mL. -What is the Limiting Reagent? -What is their theoretical yield? -What is their actual yield? -What is their percent yield? **MM of NiCl2·6 H2O = 237.70 g/mol **MM of C2H8N2 = 60.1 g/mol **MM of [Ni(en)3]Cl2 = 309 g/mol

A. C2H8N2 B. 3.47 g [Ni(en)3]Cl2 C. 2.83 [Ni(en)3]Cl2 D. 81.6%

In a similar conductimetric titration, 7.00 mL of an unknown M of NaOH was titrated with 0.115 M HCl. The equivalence point volume was 12.5 mL of HCl. -Complete the titration reaction: NaOH(aq) + HCl(aq) → ? + ? -Classify the reactants in terms of electrolytes. -Classify the products in terms of electrolytes. -As the reaction progresses, will the conductivity go up or down? -After the equivalence point, when excess HCl is added, will the conductivity go up or down? -What is the Molarity of the NaOH? *only did last part on paper

A. NaOH (aq) + HCl (aq) --> NaCl (aq) + H2O (l) B. Both reactants are strong electrolytes. C. NaCl is a strong electrolyte. H2O is a nonelectrolyte. D. As the reaction progresses, the conductivity will go down. E. After the equivalence point, when excess HCl is added, the conductivity will go up. F. 0.205 M

How would the following errors affect the calculation of mg of citric acid present per mL of juice? Will it make the values too large or too small or no effect? Explain your answers. a. Overtitrating the end point. b. Stop titrating at the first sign of pink in the solution. c. Recording that 20.0 mL of juice was titrated, when actually only 10 mL of juice was present. d. The Molarity of NaOH was recorded as 0.180 M NaOH, instead of the actual molarity of 0.109 M NaOH.

A. Overtitrating the end point would increase the mg of citric acid because the more it takes to titrate, the more suspected analyte there is. The more suspected analyte, then the more mg of citric acid present. B. To stop titrating at the first sign of pink in the solution would decrease the mg of citric acid because all of the citric acid would not have been neutralized, making the calculation of mg of citric acid inaccurate. C. Recording that 20.0 mL of juice was titrated, when actually only 10 mL of juice was present would decrease the mg of citric acid present because we would be dividing by a larger volume. D. If the Molarity of NaOH was recorded as 0.180 M NaOH, instead of the actual molarity of 0.109 M NaOH, the moles of NaOH would increase, which would cause a higher number of moles of H3C6H5O7, producing a higher mass of H3C6H5O7. The higher mass value would cause the mg of citric acid present per mL of juice to be higher.

Pierce, Manny & Ada worked together on the redox titration of H2O2 with MnO4- (Part II). Pierce & Manny used the equivalence point volume of MnO4- as determined from titration graph. However, Ada used the volume of MnO4- when the solution was dark pink, which was a larger volume than Pierce & Manny's volume. - Will Ada's calculations of the molarity of H2O2 be different than Pierce & Manny's calculation? How and why?

Ada's M of H2O2 will be higher than the other two students. Since the volume of MnO4- is in the numerator for the calculation of M of H2O2, the higher volume of MnO4- results in higher M of H2O2.

Titrations are a type of stoichiometry calculation. In this experiment what is the mole ratio between ascorbic acid and DCIP?

C6H8O6(aq) + C12H7O2NCl2(aq) --> C6H6O6(aq) + C12H9O2NCl2(aq) 1:1

When CO2(g) is bubbled through water, the carbon dioxide reacts with the H2O to form some carbonic acid, H2CO3 (aq). -Write the balanced equation for this reaction. -Classify this reaction as one of the five general types.

CO2 + H2O ---> H2CO3 - Balance equation: Already balanced - Combination reaction

5 classifications of reactions

Combinations decomposition single displacement double displacement oxidation reduction

-What was done during filtration to help reduce errors that would lead to a percent yield greater than 100% -Explain how this reduced the error

Completely filtering the solid until it is dry, because if it is wet then the actual yield will be higher, therefore percent yield would be

what is volatile and what does volatility depend on

Compounds that easily convert from liquid to gas phase are said to be volatile. Volatility of a liquid depends on its molar mass (since it affects its kinetic energy) and intermolecular forces.

- decrease - decrease -decrease; Copper(II) saccharinate is slightly soluble in warm ethanol. The solubility drops down on cooling the solution and precipitation occurs. If the cooling is not done properly a reasonable amount of the product will remain in the mother liquor.

Copper(II) saccharinate product is insoluble in cold ethanol, slightly soluble in warm ethanol, and very soluble in hot water. The procedure called for rinsing the crystals in cold ethanol, since the crystals will not dissolve. Using this information, explain what affect each of the following will have on the actual yield of the product? a) Washing the Cu(C7H4SO3N)2(H2O)4·2 H2O crystals with warm ethanol. b) Washing the Cu(C7H4SO3N)2(H2O)4·2 H2O crystals with hot water. c) Only cooling the reaction mixture to room temperature (not using the ice-bath).

Perry read the final volume of gas as 88.6 mL before aligning the water levels. His partner Ida read the final volume of gas as 91.3 mL AFTER aligning water levels. -Will Perry's calculation of percent by mass be higher or lower than Ida's? Explain your reasoning.

His will be lower because when calculating moles of O₂, you are multiplying by a lower volume, which would produce fewer moles of O₂ produced. This would cause him to calculate fewer moles of H₂O₂ and a lower molarity of H₂O₂. A lower molarity of H₂O₂ would produce a smaller % of H₂O₂by mass.

Piers & Ida performed this experiment. Both started with the exact same volume of hydrogen peroxide. However, some gas escaped out of the test tube because the rubber stopper wasn't tight in Ida's set-up. Piers did not have any errors with his experiment. Which of the following statement(s) are TRUE concerning Ida's results? I. Ida's experiment will give a lower volume of O2(g) than Piers. II. Ida's experiment will give a lower partial pressure of O2(g) than Piers. III. Ida's calculations will give a smaller molarity of H2O2 than Piers.

I and III

If you had 0.001 mol of CuSO4 in the test tube in Part II, how many moles of Cu(OH)2(s) will you form if the reaction goes to 100% completion?

IDK

Which statements explain the shape of the titration curve observed in lab? I. Initially, the conductivity is zero since the reaction has not begun. II. During the reaction, the conductivity decreases due to the production of nonelectrolytes. III. During the reaction, the conductivity decreases due increase of ions. IV. After the endpoint, the conductivity increases due to the excess titrant.

II and IV

endothermic and exothermic

In endothermic reactions, heat can be considered a reactant, since heat is absorbed from the surroundings. In exothermic reactions, heat can be considered a product, since heat is released from the system. When heat is added to an endothermic reaction, the system will shift toward products. When heat is added to an exothermic reaction, the system will shift toward reactants.

classify compounds

NaCl , KCl , Na2SO4 : strong electrolytes CH3COOH , HF : weak electrolytes glucose , alcohol , urea : non-electrolytes.

Select the redox term(s) that apply to Cl in ClO- in the half reaction below. 2 ClO- (aq) + 4 H+(aq) + 2 e - → Cl2 (g) + 2 H2O -Reducing agent -Species being oxidized -Species being reduced -Oxidizing agent

Species being reduced Oxidizing agen

what is specific heat?

Specific heat (J/g°C) is defined as the amount of heat (q in Joules) required to change the temperature of one gram of a substance by 1°C as shown in Equation 1 where ΔT = Tfinal - Tinitial.

what is meant by buffering capacity

The amount of acid (or base) that can be added before the pH value changes by +/-1 pH unit

mole fraction of a solvent

The ratio of moles of solvent to total moles in solution

In a similar experiment, Cooper, Zach & Nate started with 4.36 g of Cu(C2H3O2)2·H2O and 9.87 g of NaC7H4SO3N·H2O and obtained 10.08 g of Cu(C7H4SO3N)2(H2O)4·2H2O. -Theoretical yield of the product is? - Percent yield of product is? *Molar Mass of Copper(II) acetate monohydrate = 199.649 g/mol Molar Mass of Sodium saccharinate monohydrate = 223.18 g/mol Molar Mass of product = 535.59 g/mol

Theo = 11.763 percent = 85.7%

what are colligative properties

Those properties of the solution that depend on the number of solute molecules in the solution and not on the identity of the solute

Why do we need to subtract the water vapor pressure from the barometric pressure?

To find the partial pressure of O2

oxidation reduction

Two half-reactions added together. A→A+n+n e−B+m e−→B−mA+B→A+n+B−m(loss of electrons—oxidation)(gain of electrons—reduction) Mg→Mg+2+2 e−Co+2+2 e−→CoMg+Co+2→Mg+2+Co(oxidation)(reduction) In oxidation half reaction, one species (A) will lose electrons. Then these electrons are used in the reduction half reaction, where the other species (B) gains electrons. The number of electrons transferred must be the same in each half reaction.

What will result when water (density = 1.0 g/mL), liquid S (density = 0.65 g/mL, immiscible with H2O), and liquid T (density = 0.80 g/mL, miscible with S and immiscible with H2O) are poured into test tube?

Two layers will form in the test tube. The top layer is a mixture of liquid S & T and the bottom layer is water.

density quiz pic

Two layers will form in the test tube. The top layer is a mixture of liquid S & T and the bottom layer is water.

The mass of 3.8 mL of Solution A is 4.13 g. Determine density of Solution A.

You need the equation for density. Density = mass/mL Density = 4.13 g/3.82 mL Density = 1.08115 g/mL (next step, round to 3 significant figures) Density = 1.08 g/mL

what is a pH buffer

a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.

Explain what affect each of the following will have on the percent yield of the copper(II) saccharinate product. a) Some crystals were left behind on the filter paper. b) Spilled some of the reaction mixture while heating it on the hot plate. c) Forgot to tare the balance (subtracting out the weight of the weigh boat) when weighing the Cu(C2H3O2)2·H2O. (The initial mass of the Cu(C2H3O2)2·H2O is less than the recorded mass.)

a) Decrease the Percent Yield because some product is left on the filter paper, leading to a smaller amount of actual yield, leading to a small percent yield b) Decrease Percent Yield because some of the reactants is lost, less product can formed leading to a decrease in the actual yield, thereby decreasing percent yield c) Decrease Percent Yield because the recorded amount of Cu(C2H3O2)2·H2O is more than the initial mass, this will lead to a larger theoretical yield, and a larger theoretical yield leads to a smaller percent yield

Explain what effect each of the following will have on the actual yield of the [Ni(en)3]Cl2. -Student used 10 mL of water to dissolve the NiCl2·6 H2O. (original was 8) -Student used 12.0 mL of 4.0 M C2H8N2 but recorded the volume as 8.0 mL and used en as the limiting reagent in the calculations.

a) actual yield will decrease because NiCl2•6H2O is sensitive to large amounts of water b) actual yield will decrease because there will be less moles which will decrease the moles of en

Cooper & Zach did this experiment starting with 1.1 g of Cu(C2H3O2)2·H2O and an excess of sodium saccharinate. They recovered 2.46 g of the copper(II) saccharinate product. a) What is their actual yield? b) What is their theoretical yield? c) What is their percent yield?

a)2.46 g B)2.951 c)83.36%

- What is the partial pressure of O2 if the barometric pressure is 745.2 torr and the water temperature was 28°C? **-What is the % by mass composition of H2O2 if the Molarity of the H2O2 is 4.72 M? Assume the density of the H2O2 is 1.00 g/mL. -How many moles of O2 are present if 79.3 mL of O2 has a partial pressure of 721.8 torr at 23.7°C? -What is the Molarity of an H2O2 solution if 0.00362 moles of O2 was produced by 7.82 mL of H2O2 solution?

a)716.9 torr b)16.1% c)0.0031 moles d)0.93 M

How would the following errors affect the calculation of Molarity of H2O2? Explain your answers. -The rubber stopper with the attached hose was not fitted tightly into the test tube after the yeast was added. (Some gas escaped out of the test tube.) -The initial volume of gas in the graduated cylinder was recorded as zero instead of 3.5 mL.

a)the O₂ level would decrease as air escaped and our calculations for molarity of H₂O₂ would be lower than true value. b) This would cause you to calculate a higher value for the moles of O₂ which would lead to a higher Molarity of H₂O₂.

How would the following errors affect the calculations indicated? Will it make the values too large or too small or no effect? Explain your answers. -Overfilling the volumetric flask in determining molarity of standard ascorbic acid. -Overtitrating the end point in determining the molarity of the DCIP. -Transferring 10.00 mL of juice, but used 5.00 mL in calculating the mg of C6H8O6 present in the juice. -Overtitrating the end point in determining the mg of C6H8O6 in the fruit juice sample. -Transferring 10.00 mL of juice, but used 5.00 mL in calculating the mL required to satisfy the DRI of Vitamin C.

a. Too large. The standard solution would be too dilute. It would take more DCP to titrate the solution. b. Too large. More DCP would have been used than is necessary. c) Too small. You would multiply by a smaller number in the numerator of the last calculation. d) Too large. More DCP would have been used than is necessary. e) Too small. You would multiply by a smaller number in the numerator of the calculation.

For the following errors, determine if the error will affect the calculation of qsystem. If it does affect the calculation, then state if it will increase or decrease the value of qsystem. -Placing the hot aluminum rod on the lab bench for 30 seconds before adding it to the calorimeter. -Adding 50 mL of water, but only recording the volume of water as 30 mL. -The solid NH4NO3 did not all dissolve after adding it to the water. -Some of the HCl splashed out while pouring it into the calorimeter.

a. decreases q system b. decreases q system c. decreases q system because not all water was accounted for d. decreases q system

If the slope of the Absorbance vs concentration (in ppm) is recorded as 0.76 ppm -1 instead of the correct value of 0.67 ppm -1. Will this error affect the calculation of the concentration of an unknown solution? If so, explain why the concentration of the unknown solution will be higher or lower?

conc = absorbance/slope constant it will be smaller, you're dividing by a larger number

What solution color will be observed initially in the buret ? Colorless Pink Dark blue

dark blue

Will use of a lower Molarity value of DCIP affect the calculated mg of Vitamin C? -Decreases the value of mg of Vitamin C Correct -No effect -Increases the value of mg of Vitamin C

decreases the value of mg

How would the value of density for water be affected if the mass of the water was recorded as 5.71 g instead of 5.17 g for a volume of 5.22 mL? (Will it be higher, lower, or no effect?) Explain your answer.

higher Since density=mass/volume, the calculated density would be higher because you are dividing using a larger mass.

Le Châtelier's principle:

states that an equilibrium system will react to a change in conditions (stress) in such a way to offset the change and reestablish the equilibrium. The system will have one reaction dominating until the offsetting changes allow the rates of the forward and reverse reaction to be equal again (reestablishing equilibrium). If the forward reaction dominates in order to offset the changes, we say the system "shifts to the right" or "shifts toward products" in order to reestablish equilibrium conditions. This will increase the concentrations of the products and decrease the concentrations of the reactants. However, if the reverse reaction dominates in order to offset the changes, we say the system "shifts to the left" or "shifts toward reactants" to reestablish equilibrium conditions. This will increase the concentrations of the reactants and decrease the concentrations of the products. The changes will not return the system to the original conditions, but to a new set of conditions that establish equilibrium. The condition changes to be examined are changes that increase or decrease the concentrations of reactants or products and changes in the temperature.