Chem 1212 final
In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) Ba(OH)2
Strong electrolyte
What is the conductivity classification for an unknown D that dissolves completely in water and has a large number of ions present in solution?
Strong electrolyte
What is the conductivity classification for an unknown G that ionizes completely in water?
Strong electrolyte
Which of the following items of clothing are appropriate to wear in CHEM 1212 Lab to protect your skin ?
T-shirt, Scrub pants, Jeans, Lab Apron
Will over-filling the volumetric flask affect the "real" molarity as compared to "calculated" molarity of the standard ascorbic acid solution?
The "real" molarity will be less than the "calculated" molarity.
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 volume of O2(g)?
milliliters
What is the oxidation number of C in CO2 ?
+4
What is the oxidation number of Mn in MnO2 ?
+4
A coffee cup calorimeter contained 50.0 mL of a 1.33 M KOH solution at an initial temperature of 23.3 ºC. A student quickly add 40.0 mL of 1.54 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.
-35.4 masssoln = (mL HNO3 x 1.00 g/mL) + (mL KOH x 1.00 g/mL) ΔT = Tfinal - T initialqsoln = specific heat × masssoln × ΔT qrxn = (-) qsoln mol HNO3 = M HNO3 x L HNO3 ΔHrxn = qrxn / mol HNO3
What is the Molarity of the Ba(OH)2 solution if a 7.50 mL aliquot of the Ba(OH)2 solution required 14.30 mL of a 0.108 M H2SO4 solution to reach the equivalence point? Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(l)
0.206 M
Ferris & Mona used the ORP sensor to titrate a ferrous ammonium sulfate solution, (NH4)2Fe(SO4)2 with KMnO4 titrant. They titrated a 8.50 mL aliquot of the Fe+2 solution with 0.0207 M MnO4- solution and determined that the equivalence point was at 12.3 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
0.150 M
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
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 0.043 ppm- 1 The absorbance of the dilute unknown sports drink was 0.48 What is the concentration of this dilute unknown sports drink?
11.2 ppm
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. The theoretical yield of the product is The percent yield of the product is
11.70g 86.2%
What is the pH of a 7.5 x 10-3 M NaOH solution?
11.88
Cedrick & Astrid titrated a 15.00 mL aliquot of grapefruit juice with a 0.134 M NaOH solution to the end point. They calculated that there was 0.2042 g of citric acid present in the juice sample. What is the amount mg of citric acid present per mL of juice?
13.6 mg/mL
A 2.50 mL aliquot of a 0.10 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 8.00 mL of the first dilution and diluting it to 50.00 mL. What is the molarity of this second dilution?
1st Dilution = 0.0100 M; 2nd Dilution = 1.60 x 10-3 M
What is the pH of a 4.5 x 10-3 M HCl solution?
2.35
In a similar Exp. 9 experiment, a calibration plot of absorbance vs. concentration of Red 40 dye (ppm) was obtained with the slope of the best-fit straight line as 0.038 ppm-1The diluted unknown sports drink solution had an absorbance of 0.86. What is the concentration (ppm) of the Red 40 dye in the dilute unknown sports drink?
22.7 Absorbance = Slope × ConcentrationConcentration = Absorbance / slope
Ethyl, Ann & Ami reacted 3.33 g of NiCl2·6 H2O with 8.45 mL of 4.00 M C2H8N2. They recovered 2.47 g of product, (Ni(C2H8N2)3)Cl2. The theoretical yield of the product is The percent yield of the product is
3.49g 70.7% To find the theoretical yield: If NiCl2· 6H2O is Limiting Reagent: 1. Calculate moles of NiCl2· 6 H2O using mass of NiCl2· 6 H2O and dividing by its molar mass 2. Use that number and the mole:mole ratio to find moles of product 3. Calculate mass of product (theoretical yield) using previous number & Molar mass of the product. If ethylenediamine (C2H8N2) solution is Limiting Reagent: 1. Calculate moles of C2H8N2 using Molarity x Liters of C2H8N2: 2. Use that number and the mole:mole ratio to find moles of product 3. Calculate mass of product (theoretical yield) using previous number & Molar mass of the product. Then compare the mass of product by each reagent, whichever is the SMALLER VALUE, is the theoretical yield To find % yield: - Divide the actual or experimental yield by the theoretical yield (smaller number), and multiply by 100%
What is the pH of a buffer in which the concentration of benzoic acid, C6H5COOH, is 0.040 M and the concentration of sodium benzoate, NaC6H5COO, is 0.015 M ? Ka of C6H5COOH is 6.30 x 10-5
3.77 [H+] = 1.68E-4 pH = 3.77
What is the pH of a solution that has 0.066 M CH3COOH and 0.033 M NaCH3COO present? Ka of acetic acid = 1.80 x 10-5
4.44 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+]
Ace, Corby & Astrid dissolved 0.0531 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 5.00 mL aliquot of the standard C6H8O6 above required 14.38 mL of DCIP to reach the endpoint. What is the Molarity of the DCIP solution? A 15.00 mL aliquot of pear juice required 15.47 mL of the same DCIP solution (from above) to reach the end point. How many mg of C6H8O6 are present in the aliquot?
6.03 x 10 ^-3 M 2.10 x 10 ^-3 M 5.71 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)
An 12.0 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)?
60.0 ppm
Zach and Nate calculated the theoretical yield as 6.30 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. They recovered 4.49 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. What is the percent yield?
71.2%
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)
73.0 ppm
A red sports drink contains Red 40 dye. A 5.4 mL aliquot of this sports drink was diluted to 25.0 mL with deionized water in a volumetric flask to form a dilute drink solution. The concentration of Red 40 dye in the dilute solution was determined to be 18.1 ppm from the calibration plot. What is the concentration of Red 40 dye (ppm) in the original sports drink?
83.8 Concstock × Volumestock = Concdilute × Volumedilute Concstock = (Concdilute x Volumedilute) / Volumestock The aliquot of concentrated solution = Volumestock The diluted final volume of sample solution = Volumedilute
Cooper, Zach and Nate did this experiment dissolving 3.50 g of Cu(C2H3O2)2·H2O and adding 7.90 g NaC7H4SO3N·H2O (assume present in excess). What is the theoretical yield of the product, Cu(C7H4SO3N)2(H2O)4·2 H2O(s)?
9.39 g
Select the step(s) that will compose a rationale for the cation Bi+3 being present in an unknown.
A white precipitate formed in step 2-B., The white solid turned black upon addition of NaOH and SnCl2.
Select all the statements that are true concerning pH and buffers. A buffer works when either acids or bases are added. As a basic solution is diluted the pH increases. The smaller the concentrations of the buffer components, the greater its buffering capacity. As an acidic solution is diluted the pH increases.
As an acidic solution is diluted the pH increases. A buffer works when either acids or bases are added.
Match the correct inference to the descriptions of the reactions from the Group 3 Qualitative Analysis Experiment, A light sky blue solution formed after adding 6 M NH3 in step 3-E A yellow-tan precipitate formed in step 3-H when BaCl2 was added. When the yellow K4Fe(CN)6 solution was added in step 3-J, no precipitate formed. After the NaOH is added in step 3-A, the decantate solution is green.
A light sky blue solution formed after adding 6 M NH3 in step 3-E→ Ni+2 is indicated as present. A yellow-tan precipitate formed in step 3-H when BaCl2 was added. → Cr+3 is confirmed as present. When the yellow K4Fe(CN)6 solution was added in step 3-J, no precipitate formed. → Zn+2 is confirmed as absent. After the NaOH is added in step 3-A, the decantate solution is green. → Cr+3 is indicated as possible.
Select the step(s) that will compose a rationale for the cation Cu+2 being absent in an unknown.
A reddish brown precipitate did not form after adding K4Fe(CN)6.
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).
Adding a small amount of white NaBr(s). → Brown solution Adding a few drops of Ag+(aq) solution (Ag+ reacts with Cl- ions). → Brown solution
Select the steps that will compose a rationale for the cation Cr+3 being absent in an unknown.
After the BaCl2 was added in step 3-H, a colorless solution with no solid was present.
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the two chemical species (solid and solution) are separated from each other. What reagent could you add to a mixture of [Zn(OH)4]-2(aq) and CrO4-2(aq) to separate the two species?
BaCl2
What is the formula for barium chloride?
BaCl2
Select the correct definition or example of the following terms: Brønsted-Lowry acid Buffering capacity Neutral solution
Brønsted-Lowry acid → Any substance that donates a proton., Buffering capacity → The amount of acid or base that can be added before the pH changes by 1 pH unit., Neutral solution → A solution that has a pH of 7
In today's experiment of determining the amount of Vitamin C in fruit juice, which chemical species is the analyte?
C6H8O6 (ascorbic acid or Vitamin C)
What should you do if you spill a chemical on your lab bench?
Clean it up using the spill kit in your lab.
What should you so if you spill NaOH on the lab bench?
Clean the spill using a chemical absorbent pad from the chemical spill kit.
Match the confirmation test with a description of the positive results. Confirmation test for Bi+3 Confirmation test for Cu+2
Confirmation test for Bi+3: → a black solid, Confirmation test for Cu+2: → a maroon precipitate
Match the confirmation test with a description of the positive results. Confirmation test for Mn+2 Confirmation test for Cr+3
Confirmation test for Mn+2 → a purple solution, Confirmation test for Cr+3 → a pale yellow-tan solid
Match the confirmation test with a description of the positive results. Confirmation test for Mn+2 Confirmation test for Zn+2
Confirmation test for Mn+2 → a purple solution, Confirmation test for Zn+2 → a greyish white solid
Match the confirmation test with a description of the positive results. Confirmation test for Pb+2 Confirmation test for Ag+
Confirmation test for Pb+2 : → a yellow precipitate, Confirmation test for Ag+: → a white precipitate
Match each item to its proper disposal method. - Cracked or chipped beaker - Reaction mixture - Excess chemical - Used filter paper
Cracked or chipped beaker → Broken glass box, Reaction mixture → Appropriate waste container, Excess chemical → Appropriate waste container, Used filter paper → Trash can
In this reaction, you observed several different Cu species which had different physical attributes. Select the appropriate chemical formula(s) that corresponds to a red-brown solid.
Cu
In this reaction, you observed several different Cu species which had different physical attributes. Select the appropriate chemical formula(s) that corresponds to a black solid.
CuO
What solution color will be observed at the end point in the buret ?
Dark blue
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: Dropping the hot aluminum rod and it remains on the cold lab bench for 30 seconds before it is successfully added to the calorimeter.
Decreases the value of final Temperature
Identify the reaction type for the generic reaction given. AC + BD → AD + BC
Double Displacement
You have two test tubes. One test tube contains Fe+3(aq) solution and the other test tube contains Zn+2(aq). Predict what will happen when NaOH(aq) is added to both test tubes. If a reaction occurs, what is the new chemical formula?
Fe+3(aq) will form a brown precipitate, Fe(OH)3 (s).Zn+2(aq) will form a colorless solution, [Zn(OH)4 ]-2(aq).
You have two test tubes. One test tube contains Fe+3(aq) solution and the other test tube contains Cr+3(aq). Predict what will happen when NaOH(aq) is added to both test tubes. If a reaction occurs, what is the new chemical formula?
Fe+3(aq) will form a brown precipitate, Fe(OH)3(s).Cr+3(aq) will form a green solution, [Cr(OH)4 ]-(aq).
Which chemical(s) will be in the Erlenmeyer flask (before titration begins)?
Fruit juice, (C6H5OH)2C2O2C6H4 (phenolphthalein)
Which chemical(s) used in this experiment is/are an oxidizing agent?Check all appropriate chemicals that apply.
H2O2
In today's experiment, which chemical species is the analyte?
H3C6H5O7 (citric acid)
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the solid and solution are separated from each other. What reagent could you add to a mixture of Ag+ and Cu+2 to separate the two species?
HCl
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the solid and solution are separated from each other. What reagent could you add to a mixture of Pb+2 and Bi+3 to separate the two species?
HCl
You have one test tube which contains a colorless solution that is either Cu+2 (aq) or Pb+2(aq). Select a reagent that will allow you to differentiate between the two chemical species.If the solution is Cu+2, what will happen when the reagent is added?If the solution is Pb+2, what will happen when the reagent is added?
HCl If it is Cu+2, the solution will remain the same after adding the HCl.If it is Pb+2, a white precipitate will form after adding the HCl.
Select all that apply to an exothermic reaction.
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.
Consider the half-reactions below and determine the overall reaction. Pt(s) → Pt+2(aq) + 2 e - Cr2O7 -2(aq) + 14 H+(aq) + 6 e - → 2 Cr+3(aq) + 7 H2O 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?
How many electrons are transferred in the oxidation half-reaction? → 2 How many electrons are transferred in the reduction half-reaction? → 6 How many electrons are transferred in the overall reaction? → 6
Sid Trick titrated a 15.0 mL aliquot of juice. It required 18.23 mL of 0.0998 M NaOH to reach the equivalence point. Analyze his results and answer the questions below. The reaction and the molar mass are given below. H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(ℓ) Molar Mass of H3C6H5O7 = 192.12 g/mL How many grams of citric acid were present in the aliquot? How many mg of citric acid were present per mL of juice?
How many grams of citric acid were present in the aliquot? → 0.116 g How many mg of citric acid were present per mL of juice? → 7.77 mg/mL
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 27.33 mL of 8.64 x 10-4 M DCIP solution to reach the endpoint when titrating a 2.50 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)?
How many mg of ascorbic acid, C6H8O6, are present in the juice aliquot ? → 4.16 How many mL of this juice would Bich have to drink in order to meet the Daily Recommended Intake (DRI)? → 54.1
In the redox reaction below, identify and match each reactant to their function. S2O8−2 (aq) + I2(s) → 2 I− (aq) + S4O6−2 (aq)
I2(s) → Species being reduced S2O8−2 (aq) → Species being oxidized
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 increase of Ba+2 and OH- ions. III. At the equivalent point, the conductivity is nearly zero since all the Ba+2 and OH- ions have reacted to produce nonelectrolyte products. IV. After the endpoint, the conductivity increases due to the excess titrant.
III and IV are TRUE.
Match the correct inference to the description of the reactions from the Group 1 & 2 Qualitative Analysis Experiment. In step 1-A after adding the 6 M HCl to an unknown, a white precipitate formed with a colorless decantate. In step 1-D, after the 6 M NH3 was added, the white precipitate dissolved creating a colorless solution. Then, after the addition of 6 M HNO3 (and the solution tested acidic), a white precipitate formed. In step 1-C, after adding the CH3COOH and K2CrO4, the colorless solution turned yellow and no solid formed.
In step 1-A after adding the 6 M HCl to an unknown, a white precipitate formed with a colorless decantate. → Ag+ and Pb+2 are indicated as possibly present. In step 1-D, after the 6 M NH3 was added, the white precipitate dissolved creating a colorless solution. Then, after the addition of 6 M HNO3 (and the solution tested acidic), a white precipitate formed. → Ag+ is confirmed as present. In step 1-C, after adding the CH3COOH and K2CrO4, the colorless solution turned yellow and no solid formed. → Pb+2 is confirmed as absent.
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 overall pressure of the equilibrium system. Increasing the overall temperature of the equilibrium system.
Increasing the overall pressure of the equilibrium system. → Will shift the equilibrium towards the reactants. Increasing the overall temperature of the equilibrium system. → Will shift the equilibrium towards the products.
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.
Increasing the partial pressure of carbon monoxide gas. → Will shift the equilibrium towards the reactants. Decreasing the overall total pressure of the equilibrium system. → Will shift the equilibrium towards the products.
Match the definitions to the appropriate Chemical Alert terms. - Irritant - Carcinogen - Toxic - Corrosive
Irritant → chemical causes dryness, itching or sensitivity Carcinogen → chemical suspected or proven to cause cancer Toxic → may cause harm through ingestion, inhalation or skin absorption Corrosive → irreversibly destroys living tissue or metal upon contact
You have one test tube which contains a solution that is either Ni+2(aq) or Fe+3(aq). Select a reagent that will allow you to differentiate between the two chemical species. If the solution is Ni+2(aq), what will happen when the reagent is added? If the solution is Fe+3(aq), what will happen when the reagent is added?
KSCN If it is Ni+2(aq), the green solution will stay the same after adding the KSCN.If it is Fe+3(aq), the blood red solution will form after adding the KSCN.
For the procedural error, indicate if the error will affect the actual yield of [Ni(C2H8N2)3]Cl2 product and if it does, will it raise or lower the actual yield: Dissolving the NiCl2·6 H2O in 12 mL of water initially
Lowers the actual yield
For the procedural error, indicate if the error will affect the actual yield of copper(II) saccharinate product and if it does, will it raise or lower the actual yield: Leaving some crystals behind in the beaker
Lowers the actual yield
For the procedural error, indicate if the error will affect the actual yield of copper(II) saccharinate product and if it does, will it raise or lower the actual yield: Spilling some of the sodium saccharinate while transferring the solid to the beaker
Lowers the actual yield
Will overtitrating the end point in Part II affect the value of Molarity of DCIP?
Lowers the value of Molarity of DCIP
Where is the eye wash station located?
Mounted on the wall next to the large sink.
Can you eat or drink in the lab?
NO
Select all the chemical species that are moisture sensitive.
NaBiO3
You have one test tube which contains a solution that is either Ni+2 (aq) or Fe+3 (aq).Select a reagent that will allow you to differentiate between the two chemical species. If the solution is Ni+2 (aq), what will happen when the reagent is added? If the solution is Fe+3 (aq) what will happen when the reagent is added?
NaOH If it is Ni+2(aq), a green precipitate will form after adding the NaOH. If it is Fe+3 (aq), a gold-brown precipitate will form after adding the NaOH.
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the two chemical species (solid and solution) are separated from each other. What reagent could you add to a mixture of Mn+2(aq) and Cr+3(aq) to separate the two species?
NaOH, BaCl2
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? Adding 20 mL of water to the Erlenmeyer flask before titration
No effect
In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) BaSO4
Nonelectrolyte
A common error in titration is over-titrating. Which of the following statement(s) is/are TRUE for the citric acid titration? I. Over-titrating means too much titrant was added to the reaction. II. Since the volume of titrant is too large, dividing by this larger number in the calculation of citric acid makes the mass of citric acid too low. III. Over-titrating means too much aliquot was added to the reaction.
Only I is TRUE.
Which of the following statements are TRUE if the titration of fruit juice (Part III) was under-titrated? I. The amount of Vitamin C will be lower since the smaller volume of DCIP is in the numerator in the Vitamin C calculation. II. Too little DCIP was added in the titration, causing the Molarity of the ascorbic acid to be lowered. III. The amount of Vitamin C would be higher since under-titrating makes the Molarity of DCIP higher and the Molarity of DCIP is in the numerator of the Vitamin C calculation.
Only I is TRUE.
Match the correct definition or example to each item. Overall Reaction Rate Rate Determining Step
Overall Reaction Rate → Rate of the slowest step., Rate Determining Step → Step in the reaction mechanism that has the slowest rate.
Identify the reaction type for the generic reaction given. A + B → A+n + B-m
Oxidation-Reduction
What color is expected for the product, [Ni(C2H8N2)3]Cl2 (s), if C2H8N2 is the limiting reagent?
Pink-violet
For the procedural error, indicate if the error will affect the actual yield of [Ni(C2H8N2)3]Cl2 product and if it does, will it raise or lower the actual yield: Weighed the product while the product was still wet
Raises the actual yield
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? Over-titrating the end point (adding too much titrant)
Raises the value of mg citric acid/mL juice
In the generic reaction below, experimental data indicate the reaction is third order in A, first order in C and rate constant is 5.4 x 10 -3 M -1sec -1. Which is the correct rate constant expression? A(aq) + 3 C(aq) → AC3(aq)
Rate = (5.4 x 10 -3 M -1sec -1) [A]3 [C]
What must you do before coming to the lab?
Read the experiment. Take the Lab Quiz. Prepare lab notebook for the experiment. Write the Chemical Alert Table in the lab notebook. Review the chemicals and their hazards.
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)
Red
Which of the following are appropriate to wear in CHEM 1212 Lab to protect your feet?
Sneakers or tennis shoes, Boots, Loafers
Select the redox term(s) that apply to I in I2 in the half reaction below. I2(s) + 2 e - → 2 I- (aq)
Species being reduced, Oxidizing agent
Nick and Kel reacted 2.80 g of NiCl2· 6 H2O with 7.00 mL of 4.00 M C2H8N2. They recovered 2.40 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 actual or experimental yield is ... The chemical, NiCl2· 6 H2O, is the ... The theoretical yield is ... The chemical, C2H8N2, is the ...
The actual or experimental yield is ... → 2.40 g The chemical, NiCl2· 6 H2O, is the ... → chemical present in excess The theoretical yield is ... → 2.89 g The chemical, C2H8N2, is the ... → limiting reagent
What is the correct definition of specific heat?
The amount of heat required to change the temperature of one gram of substance by 1°C.
Which definition corresponds to theoretical yield?
The amount of product that could be produced using a given amount of reactant.
Which definition corresponds to a titrant?
The chemical species being added in a titration.
Select the step(s) that will compose a rationale for the cation Zn+2 being present in an unknown.
The colorless decantate was isolated in step 3-H when BaCl2 was added., A grey-white solid formed in step 3-J.
Consider the benzoic acid dissociation reaction below which is at equilibrium.C6H5COOH (aq) + H2O(ℓ) ⇋ C6H5COO-(aq) + H3O+(aq) If some strong acid is added (which donates H3O+, hydronium ion) is added to the system (stress), how will the system change in order to re-establish equilibrium? Select all that might apply.
The concentration of C6H5COO- will decrease., The concentration of C6H5COOH will increase.
Which statement about the spectrophotometric analysis of Red 40 dye is TRUE?
The intensity of the color of the solution is directly proportional to concentration of the Red 40 dye.
If an error caused the final temperature to be larger, how does this affect the calculation of the heat of solution (qsolution)?
The larger Tfinal would produce a larger ΔT, which would result in a larger q.
Which definition corresponds to limiting reagent?
The reactant that is completely consumed during the reaction.
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 the reaction is exothermic and it is placed in hot water bath. Then explain what will occur in terms of Le Châtelier's principle.
The solution will become a lighter blue solution.The system must shift towards reactants to remove the excess heat because heat acts as a product.
A reaction mixture was formed by adding 55 mL H2O, 10.0 mL of 0.66 M H2O2, and 5.0 mL of 0.40 M KI. What is the molarity of the H2 O2 in the reaction mixture? What is the molarity of the KI in the reaction mixture?
What is the molarity of the H2 O2 in the reaction mixture? → 0.094 M What is the molarity of the KI in the reaction mixture? → 0.029 M
Which statement best explains what happens to the percent yield if the initial mass of Cu(C2H3O2)2·H2O (reactant) is less than its recorded mass due to forgetting to tare the weigh boat?
The theoretical yield will be greater since there is theoretically more reactant to form products. Since theoretical yield is in the denominator, the percent yield will decrease.
Match each item to its proper disposal method.
Used filter paper → Trash can, Reaction mixture → Appropriate waste container, Excess chemical → Appropriate waste container, Cracked or chipped beaker → Broken glass box, Used (and rinsed) Beral pipet → Trash can
What should you do if some of the H2O2-H2SO4 solution comes into contact with your skin?
Wash the skin for 15 minutes with water and notify the TA.
Predict the conductivity of NH2(CH3), a weak base.
Weak electrolyte
What is the conductivity classification for an unknown E that dissolves completely in water and only has a few of ions present in solution?
Weak electrolyte
When 5.73 g of CaCl2 dissolved in 50.00 mL of water in a coffee cup calorimeter, the temperature of the solution rose from 23.4°C to 28.6°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 ?
What is qsolution? → (+) 1210 J, What is qreaction ? → (-) 1210 J, What is ΔHrxn in kJ/mol of CaCl2 ? → (-) 23.5 kJ/mol
In the redox reaction seen earlier this semester and described below, determine the oxidation numbers of the selected chemical species and then determine what is the reducing agent and the oxidizing agent . In a basic solution, Bi+3 (aq) reacted with SnCl2 to form Bi(s) and SnCl4(aq). What is the oxidation number of Sn in SnCl2 ? What is the oxidation number of Bi? In this redox reaction, what is the role of SnCl2? In this redox reaction, what is the role of Bi+3 ? What is the oxidation number of Sn in SnCl4 ?
What is the oxidation number of Sn in SnCl2 ? → +2, What is the oxidation number of Bi? → 0, In this redox reaction, what is the role of SnCl2? → Reducing agent, In this redox reaction, what is the role of Bi+3 ? → Oxidizing agent, What is the oxidation number of Sn in SnCl4 ? → +4
Consider an experiment where 6.25 mL of an unknown H2O2(aq) solution reacted with the yeast at 25.2°C to produce 75.16 mL of gas. The barometric pressure was 740.3 torr. The vapor pressure of H2O is 23.8 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?
What is the partial pressure of O2 (in atm) in the collected gas? → 0.9458 atm O2 How many moles of O2 were produced by the reaction? → 0.002894 mol O2 How many moles of H2O2 reacted to produce this amount of O2 ? → 0.005788 mol H2O2 What is the Molarity of the H2O2 solution? → 0.926 M H2O2
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. Their calculation of (6.88 g/9.28 g) x 100% is equal to 74.1%. What is the percent yield ? What is the actual yield? What is the theoretical yield ?
What is the percent yield ? → 74.1, What is the actual yield? → 6.88, What is the theoretical yield ? → 9.28
Cedrick & Astrid titrated a 25.00 mL aliquot of grapefruit juice with a 0.117 M NaOH solution to the end point. The initial buret reading was 1.82 mL and the final buret reading was 21.33 mL. H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(l) What is the volume of NaOH titrated? What is the mass of citric acid in the juice sample?
What is the volume of NaOH titrated? → 19.51 mL What is the mass of citric acid in the juice sample? → 0.146 g To calculate the Volume of NaOH titrated into the flask is: Final Buret volume - Initial Buret Volume = volume titrated To find mass of Citric acid in the juice, you need to: Calculate the moles of NaOHM NaOH x Vol. NaOH titrated = moles NaOH reacted Calculate the moles of Citric Acid (H3C6H5O7)mole NaOH reacted x [1 mol H3C6H5O7 / 3 mol NaOH] = mol of H3C6H5O7 Calculate the mass of H3C6H5O7mol of H3C6H5O7 x Molar Mass of H3C6H5O7 = mass of H3C6H5O7
When is it okay to remove your chemical splash proof goggles?
When everyone in the lab has put away all chemicals and glassware.
Match the appropriate response to the following questions. Some answers may be used more than once. What should you do if a . . . - chemical is splashed on your leg? - chemical is spilled on your hand? - person's hair or clothing catch fire? - chemical gets into your eye?
chemical is splashed on your leg? → Remove affected clothing and rinse with running water for 15 minutes. chemical is spilled on your hand? → Rinse with running water for 15 minutes. person's hair or clothing catch fire? → Wrap with a fire blanket and then Stop, Drop & Roll. chemical gets into your eye? → Flush with eye-wash solution for 15 minutes.
From the description of the reaction below, balance the equation and also select the classification of the reaction. When colorless soluiton of AgNO3 (aq) reacts with a solid steel wool, Fe(s), it forms metallic Ag (s) and a light gold solution of Fe(NO3)3 (aq) over the solid. Fe (s) + AgNO3 (aq) → Fe(NO3)3 (aq) + Ag (s) coefficient in front of Fe(NO3)3 (aq)... coefficient in front of AgNO3 (aq)... Classification of reaction... coefficient in front of Ag (s)... coefficient in front of Fe (s)...
coefficient in front of Fe(NO3)3 (aq) → 1 coefficient in front of AgNO3 (aq) → 3 Classification of reaction → Single displacement coefficient in front of Ag (s) → 3 coefficient in front of Fe (s) → 1
What is the name for NaBiO3 (s) ?
sodium bismuthate
Predict the conductivity of H2SO4, a strong acid.
strong electrolyte
In a certain reaction, a solid chemical dissolved in water. The temperature of the water sample raised from 25.4 °C to 30.3 °C. From this description of the experiment, select the correct words to fill the blanks. The water is defined as the... The system ... heat qsystem has a .... value The reaction is an .... reaction
surrounding lost negative exothermic Heat is abbreviated as q and is calculated as: q = specific heat × mass × ΔT.In the coffee cup calorimeter, we monitor the T of the water (surroundings). Then we calculate the qsurroundings using the equation above. Next we use the relationship that the heat lost (or gained) by the surroundings is the heat gained (or lost) by the system. The value of qsystem is the same as qsurroundings, but opposite in sign. Mathematically this is expressed as: qsurroundings = (-) qsystem If qsystem is a (+) value, then heat is entering into the system from the surroundings.The reaction is classified as an endothermic reaction. If qsystem is a (-) value, then heat is exiting from the system and going to the surroundings.The reaction is classified as an exothermic reaction. In this reaction, the chemical reaction is the system and the water is the surroundings. The temperature of the surroundings increases. So heat is leaving (exiting) the system and going into the surroundings. (The system loses heat and the surrounding gains heat.)So qsurroundings will be a (+) value, but qsystem will be a (-) value and thus it is an exothermic reaction.
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?
torr
