Chem Lab Practical Study Guide

Calculate the molality of a sugar solution that contains 3.94 g sucrose (C12H22O11) dissolved in 285 g water.

.0404 m

Potassium hydrogen phthalate (KHP, molar mass = 204.22 g/mol) is often used as a primary standard in acid-base titration. If 20.05 mL of NaOH is required to neutralize 0.412 g of KHP, what is the concentration of the NaOH?

.101 M

Potassium hydrogen phthalate (KHP) is often used as a primary standard in acid-base titration. If 20.35 mL of NaOH is required to neutralize 0.457 g of KHP, what is the concentration of the NaOH?

.110 M

The concentration of a dilute aspirin solution is 0.000503 M. Standard solutions of this compound were used to prepare a Beer\'s Law plot which gives a slope of 1550.8 M-1. What is the expected absorbance value for the aspirin solution?

.78

For the oxidation-reduction reaction equation given here, 2K + F2 ---> 2KF indicate how many electrons are transferred in the formation of one formula unit of product.

1

The reaction A+B --> C+D has initial rate of 0.0690 M/s rate = k[A][B]^2 1) What will the initial rate be if [A] is halved and [B] is tripled? 2) What will the initial rate be if [A] is tripled and [B] is halved?

1) .311 M/s 2) 5.18*10^-2 M/s

1) A 0.0000745 M sample of Compound X in a solvent has an absorbance of 0.374 at 528 nm in a 1.000-cm cuvet. The solvent alone has an absorbance of 0.063. What is the molar absorptivity of Compound X? 2) A different sample of Compound X in the same solvent has an absorbance of 0.463 at 528 nm when measured with the same cuvet. What is the concentration of this second sample?

1) 4.17*10^3 M^-1*cm^-1 2) 9.58*10^-5 mol X/L

Suppose you generate the following spectroscopic data for two different concentrations of a solution. Concentration (M) 0.0139 and 0.1261 Absorbance 0.1131 and 0.6015 1) What is the slope of the line formed by these points? 2) What is the y-intercept? 3) What is the concentration of a solution with an absorbance of 0.393?

1) 4.3529 2) .05259 3) .0782

Calculate pH for each H+ concentration: 1) 1*10^-6 M 2) 0.01 M 3) 1*10^-12 M

1) 6 2) 2 3) 12

Match the missing symbol, name, or unit to the variables in the Beer-Lambert Law (Symbol, Name and Units)

1) A - absorbance - no units 2) ε - molar absorptivity - L/(mol*cm) 3) b - path length - cm 4) c - concentration - mol/L

Construct the following SI derived unit, the coulomb, and define the faraday.

1) A coulomb is a measure of electric charge and has units of: 1 A*s 2) A faraday is a constant and has a value of: 96485 C/mole of electrons (include units)

1) Specific protocol should be followed any time a balance is used to weigh the mass of a chemical or object. Select which of the following rules are part of this protocol. 2) Why should these selected rule(s) be followed?

1) A. Glassware must be dried thoroughly before being weighed. B. Glassware, containers, and chemicals should be at room temperature. C. All chemicals should be contained in either a piece of glassware or weighboat. D. The same balance should be used throughout an experiment. E. Filter paper must be completely dry, even after being used in an experiment. 2) Objects at any temperature other than room temperature can create air currents which can affect the balance pan, causing the measured mass to be higher or lower than the true mass, There may be discrepancies in accuracy between individual balances, A residue left on the balance will contaminate the balance pan surface and anything that comes into contact with it afterwards, and Weighing wet items will cause the displayed mass to be greater than the actual mass of the object.

Classify each as either Acid or Base 1) CH3CH2NH3+ 2) C6H5OH 3) CH3CH2O-

1) Acid 2) Base 3) Acid

The Fajans titration uses an adsorption indicator to detect the endpoint of a titration in which a precipitate is formed. For the titration of Cl- by Ag insoluble AgCl is formed. Indicate what is happening at each step of the titration by selecting the correct statement. 1) During the titration: 2) At the endpoint, just past the equivalence point: 3) Detection of the endpoint by a dye color change:

1) Ag solution is added to Cl- solution. 2) An excess of Ag ions imparts a positive charge to the surface of the precipitate. 3) An anionic dye binds to the positive surface of the precipitate.

Identify the oxidized substance, the reduced substance, the oxidizing agent, and the reducing agent in the following redox reaction: 3Ni2+ +2Co ----> 2Co3+ +3Ni 1) Which substance gets oxidized? 2) Which substance gets reduced? 3) What is the oxidizing agent? 4) What is the reducing agent?

1) Co 2) Ni2+ 3) Ni2+ 4) Co

Part I: Using the figure below as a reference to what you know about solutions, determine the appropriate relationship between the color of a solution prepared with a highly colored solute and that solution\'s concentration. Part II: If the following concentration values are given to these glasses of liquids, identify the approximate concentration of Unknown A by placing the correct concentration from the standard solutions in the bin under the unknown liquid.

1) Concentration is directly proportional to the deepness of a solution's color 2) Unknown A - 0.100 M

Maintaining the integrity of the stock reagents is a constant concern in the lab environment. Read the following situations and decide if each represents a valid contamination concern. 1) A student uses a pipet designated for the NaOH solution to pipet the H2SO4 solution. 2) Several students have left-over reagents after the completion of an experiment and decide to return the excess reagents to their original containers. 3) Only one spatula is available to measure out several different white powders. 4) Rather than wasting multiple weigh boats, a student decides to wash and dry a single weigh boat in-between uses. 5) A group of students must use the same 500 mL volumetric flask to make solutions. 6) Between each use they wash and dry the flask. At the end of the day, the waste bottle is so full that a student decides to dump his waste into an almost empty bottle of stock KI solution.

1) Contaminates 2) Contaminates 3) Contaminates 4) Does not contaminates 5) Does not contaminates 6) Contaminates

Identify the oxidized substance, the reduced substance, the oxidizing agent, and the reducing agent in the following redox reaction: Cu + 2AgNO3 ----> 2Ag + Cu(NO3)2 1) Which substance gets oxidized? 2) Which substance gets reduced? 3) What is the oxidizing agent? 4) What is the reducing agent?

1) Cu 2) Ag+ 3) Ag+ 4) Cu

Read the following statements, then classify each as true or false. 1) An effective way to test the amount of red dye in an aqueous solution is to measure the amount of white light (400-700 nm) absorbed by the solution. 2) An effective way to test the amount of red dye in an aqueous solution is to measure the amount of green light (495-570 nm) absorbed by the solution.

1) False 2) True

Determine which statements below are true and which are false. 1) PAH is an acronym for phosphorus antimony hydrogen. 2) PAHs interact with bentonite clay by intercalating into the pores. 3) Bentonite clay sequesters PAHs by the formation of permanent covalent bonds.

1) False 2) True 3) False

Select the term that makes each statement true. 1) An oxidizing agent _____ electrons 2) A reducing agent ____ electrons 3) Fe3+ is formed by the ____ of Fe 4) Br- is formed by the ____ of Br

1) Gains 2) Loses 3) Oxidation 4) Reduction

1) Write the balanced chemical equation for the reaction of the weak acid HCN with water. Include the phase of each species. 2) Complete the Ka expression for this reaction.

1) HCN (aq) + H2O(l) --> H3O+(aq) + CN-(aq) 2) Ka = [H3O+][CN-]/[HCN]

1) Suppose the percent transmittance of a solution of Procion Red is measured. If adding bentonite clay sequesters dye molecules from solution, removing the clay would cause the measured percent transmittance to ____________ 2) Consider what would happen if absorbance were monitored rather than percent transmittance in the previously described scenario. Removing the clay from solution would cause the measured absorbance to ____________

1) Increase 2) Decrease

1) What is the oxidation state of each element in K2Cr2O7? 2) What is the oxidation state of each element in SO32-?

1) K = +1, Cr = +6, and O = -2 2) S = +4 and O = -2

Determine the concentrations of MgCl2, Mg2 , and Cl- in a solution prepared by dissolving 2.22 × 10-4 g MgCl2 in 2.25 L of water. Express all three concentrations in molarity. Additionally, express the concentrations of the ionic species in parts per thousand (ppt).

1) MgCl2 = 1.04*10^-6 M 2) Mg2+ = 1.04*10^-6 M = 2.50*10^-5 ppt 3) Cl- = .07*10^-6 M = 7.38*10^-5 ppt

What is the oxidation state of each element in Mn(NO3)2?

1) Mn = +2 2) N = +5 3) O = -2

The indicator thymol blue has two color transitions as indicated in the table at the right. Select the color expected when thymol blue is added to solutions having the following pH values. 1) pH 1 2) pH 2 3 pH 6 4) pH 10

1) Red 2) Orange 3) Yellow 4) Blue

Determine the correct sequence of steps used in carrying out a measurement using a pH probe. Rank them in order from first to last. All of the steps must be placed.

1) Remove prove from storage solution 2) Rinse probe with deionized or distilled water and blot dry 3) Place probe in solution to be measured 4) Observe readout on meter or sample solution pH 5) Rinse probe, blot dry, then place in storage solution

1) Volumetric pipets come in a variety of sizes typically ranging from 0.5 mL to 200.0 mL. Select the following instances in which a volumetric pipet would be the best choice of glassware 2) Based on the choices you selected above, why would a volumetric pipet be used? 3) Why would a volumetric pipet not be used in the other situations?

1) To create a 200.0 mL of a 0.10 M H2CO3 solution from a 6 M solution of H2CO3 and To prepare a set of diluted HCl solutions requiring volumes of exactly 1.0, 5.0, and 10.0 mL 2) A volumetric pipet would precisely deliver the proper amount of solution. 3) There are other pieces of glassware better suited for these tasks.

An iodine clock kinetics experiment was performed by varying the composition of reactant solutions and measuring resulting rates of reaction. (Chart LOOK AT SAPLING) 1) How do trial 2 and 3 in the above table differ? More than one response is possible. 2) Which of the four proposed mechanisms below would be supported by these results? Note: there may be more than one answer. (scroll down to see all four proposed mechanisms)

1) Trial 2 has twice as much I- as Trial 3 and Trial 3 has twice as much S2O82- as Trial 2 2) Proposed mechanism 2

Research funding is often obtained by preparing and submitting a grant proposal to a government agency. Decide if the following statements regarding this process are true or false. 1) Agencies typically award funds based upon which proposals are deemed the best investments. 2) A proposal that has been submitted is virtually guaranteed to be awarded funding.

1) True 2) False

You need to prepare 250. mL of a 0.850 M aqueous solution of a pure solid with a molar mass of 295.2 g/mol. 1) Which type of glassware should you use to make this solution (assuming that the accuracy of the concentration is important)? 2) How should the correct amount of solute be obtained? 3) Based on your answer above, what is the value of x? 4) How should the solute and solvent be mixed in the container?

1) Volumetric Flask 2) Measure out x g of the solid on a balance. 3) x = 62.73 4) Mix a small amount of water with the solute to dissolve it, then fill with water to the 250-mL mark.

1) A student must make a buffer solution with a pH of 3.0. Determine which of the acids and conjugate bases listed below are the best options to make a buffer at the specified pH. 2) The final volume of buffer solution must be 100.00 mL and the final concentration of the weak acid must be 0.100 M. Based on this information, what mass of solid conjugate base should the student weigh out to make the buffer solution with a pH=3.0?

1) Weak acid: formic acid, Ka=1.77x10-4 1) Conjugate bases: sodium formate HCOONa 2) .120 grams

For the reaction X ---> Y identify what the graphs of [X] versus time and [Y] versus time would look like for various orders.

1) Zero-order [X] vs t (downward slope) 2) Zero-order [Y] vs t (upward slope) 3) First or Second-order [X] vs t (Downward gradual slope) 4) First and Second-order [Y] vs t (Upward gradual slope)

For each reaction, identify the precipitate or lack thereof. 1) 2NaCl + Ba(OH)2 ---> BaCl2 + 2NaOh 2) AgClO3 + MgI2 ---> AgI + Mg(CIO3)2

1) no precipitate 2) AgI

During operation, which half-reaction occurs at the cathode in each type of cell? 1) In a battery (voltaic or galvanic cell) 2) In an electrolytic cell

1) reduction occurs at the cathode 2) reduction occurs at the cathode

Complete each statement on grant proposals by filling in the correct term. 1) A typical grant proposal is divided into three sections: 2) The long-term objectives of a research study are presented in the _____ section 3) The importance of a research study is explained in the _____ section. 4) The procedure proposed for carrying out the research study is described in the ____ section.

1) specific aims, background and significance, and methods 2) specific aims 3) background and significance 4) methods

Label the pH scale below, indicating the acidity of a solution in the given regions. (Acidic - 1 and Basic - 14) Indicate the color of bromothymol blue within the pH ranges shown below using information on common indicators. 1) pH <= 6 2) pH = 7 3) pH >= 8

1) yellow 2) green 3) blue

You need to determine the concentration of a sulfuric acid solution by titration with a standard sodium hydroxide solution. You have a 0.1132 M standard solution. You take a 25.00 mL sample of the original acid solution and dilute it to 250.0 mL. You then take a 10.00 mL sample of the dilute acid solution and titrate it with the standard solution. You need 18.73 mL of the standard solution to reach the endpoint. What is the concentration of the original acid solution?

1.06 M

The concentration of a solution can be expressed in a number of ways. Choose the solution expressions that are equal to a solution that contains 1 mg/mL solute.

10-3 mg/μL, 103 μg/mL and 1 g/L

8.80 g of NH4Cl is added to 15.6 g of water. Calculate the molality of the solution.

10.5 m Nh4Cl

You have 37.0 mL of a 0.400 M stock solution that must be diluted to 0.100 M. Assuming the volumes are additive, how much water should you add?

111 mL

What is the minimum amount of time an area of a person's body, that has been exposed to harmful chemicals, should be washed?

15 minutes

The dartboards below represent molecules of two different substances in separate solutions. The darts thrown at the boards represent photons of light passing through the solutions. As more photons pass through a solution, the solution with the higher molar absorptivity will absorb more of the passing photons. Label each of the images below according to the molar absorptivity the substance would be associated with.

2 M Solution of substance A: low molar absorptivity 2 M Solution of substance B: high molar absorptivity

Suppose you generate the following spectroscopic data with five solutions of known concentration. (Chart CHECK SAPLING) If the concentration is on the x-axis, what is the slope of the line formed by these points?

4.4

A solution of a specific vitamin has λmax = 269 nm and a concentration of 2.61 × 10-7 M. The absorbance of the solution at 269 nm is A = 0.135. What is the molar absorptivity of the vitamin at 269 nm? (sample pathlength = 1.00 cm)

5.17*10^5 L mol^-1 cm^-1

Based upon the absorbance spectrum of Red dye #40, what would be the ideal wavelength to carry out a spectrophotometric experiment on the dye?

503 nm (peak of the graph)

How many milliliters of 11.0 M HCl(aq) are needed to prepare 735.0 mL of 1.00 M HCl(aq)?

66.8 mL

Solve the Beer's Law equation below for molar absorptivity, ε, by filling in the following equation:

A = ε*b*C ε units = L/mol*cm

A spectrophotometer measures the transmittance or the absorbance, or both, of a particular wavelength of light after it has passed through a liquid sample. The liquid sample holder is commonly known as a cuvette. Before the transmittance or absorbance of the sample is measured, a cuvette filled only with solvent, called the blank, is placed in the spectrophotometer. Select the statement from the following that is true for why is a blank measured before the sample.

A blank is measured to remove the signal caused by the cuvette walls and solvent.

You are measuring the concentration of Fe2 in a sample by measuring the absorbance of its complex with ferroxine. Your sample, measured in a 1.00-cm pathlength cuvette, has an absorbance of 0.205 while the reagent blank in the same cuvette has an absorbance of 0.034. What would be the absorbance reading of these two solutions if measured in a cuvette with 8.00 cm pathlength?

A sample = 1.64 A reagent blank = .272

A buffer solution is made using a weak acid, HA, that has a pKa of 6. If the pH of the buffer is 8, what is the ratio of A- to HA?

A-/HA = 1*10^2

Acid or Base? (CF3COOH) + (H2O) = (H3O+) + (CF3COO-)

Acid: CF3COOH and H3O+ Base: H2O and CF3COO-

Acid or Base? HBr, (CH3)2C=OH+, CH3CH2NH2

Acid: HBr and (CH3)2C=OH+ Base: CH3CH2NH2

Select the statement that describes a galvanic (voltaic) cell.

An electrochemical cell that produces electricity from a spontaneous oxidation-reduction reaction.

Arrhenius Bases: NH3, Br-, NaOH Bronsted-Lowry Bases: NH3, Br-, NaOH Lewis Bases: NH3, Br-, NaOH

Arrhenius/Bronsted-Lowry: NH3 and NaOH Lewis Bases: NH3, Br-, NaOH

Rank these species by their ability to act as an oxidizing agent. F2, Sn2+, Cr2+, and Al3+

Best oxidizing agent: F2, Sn2+, Cr2+ and Al3+

Please select the reasons why you do not discard broken glassware in regular garbage or recyling containers. (Select all correct responses)

Broken glassware could still contain chemicals that need to be disposed of properly. and Potential injuries could occur if janitorial staff do not see broken glassware.

Which of the following elements is not found in zeolite? C, Al, Si or Na

C

Triiodide is formed by the following exothermic reaction. I2 + I- and forms I3- Which of the following would cause the equilibrium of this reaction to shift to the right?

Cooling the system and addition of I-

How can you experimentally determine the pKa of acetic acid?

Determine the pH of the solution half way to the end-point on the pH titration curve for acetic acid.

During a spectrophotometric analysis of an unknown, you measure your unknown solution\'s absorbance, and the value is higher than the highest standard you used to make your standard curve. What should you do to make sure you can use your standard curve to determine the unknown\'s concentration?

Dilute the unknown so that it will have an absorbance within the standard curve. Once the diluted unknown concentration is determined, the full strength concentration can be calculated if the dilution process is recorded. Beer\'s Law only applies to dilute solutions, so diluting the unknown is better than making new standards.

Calculate the E°cell for the following equation. Use these standard potentials . Cu + Ag+ ---> Cu+ + Ag

Ecell = .28 V

A galvanic (voltaic) cell consists of an electrode composed of chromium in a 1.0 M chromium(III) ion solution and another electrode composed of copper in a 1.0 M copper(II) ion solution, connected by a salt bridge. Calculate the standard potential for this cell at 25 °C. Standard reduction potentials can be found here.

Ecell = 1.08 V

Calculate the E°cell for the following equation. Use these standard potentials Sn + F2 ---> Sn2+ + 2F-

Ecell = 3.01 V

A voltmeter is primarily used to measure

Electrical potential

Classify each of the following substances and descriptions as an electrolyte or a nonelectrolyte. Note: If any part of this question is answered incorrectly, a single red X will appear indicating that one or more substances have been placed incorrectly.

Electrolyte: a soluble ionic compound, NaCl, Kl, NaOH Nonelectrolyte: most molecular solutes, a substance that forms an aqueous solution that does not conduct electricity, table sugar, CH3OH

What effect does increasing the concentration of a dissolved solute have on each of the following colligative properties?

Elevation: Boiling Point Depression: Freezing Point and Vapor Pressure

Which of the following describes the recommended method for proper eye protection in a laboratory setting for a student who needs eye glasses or contacts to see well?

Eye glasses under goggles

The cage size of the zeolites is in cm scale.

False

The idea of further converting the zeolite to be magnetic is to make the zeolite more stable.

False

Zeolites are used as absorbents only and have no other uses.

False

Zeolites do not have large surface areas, instead, they have cage-like empty space.

False

Which of the following is true of an isosbestic point?

It is a point on an absorption spectra where two species have the same molar absorptivity.

For the reversible reaction: A and B Which K values would indicate that there is more B than A at equilibrium?

K = 2*10^7 and K = 2000

For the following reaction: KClO ----> KCl+1/2O2 assign oxidation states to each element on each side of the equation.

K react/prod: 1/1 Cl react/prod: 1/-1 O react/prod: -2/0 O is oxidized Cl is reduced

A monoprotic acid, HA, is dissolved in water: HA + H2O = H3O+ + A- The equilibrium concentrations of the reactants and products are [HA] = 0.170 M [H3O ] = 2.00 × 10-4 M [A-] = 2.00 × 10-4 M Calculate the Ka value for the acid HA.

Ka = 2.35*10^-7

The Ka values for several weak acids are given below. Which acid (and its conjugate base) would be the best buffer at pH = 6.0?

MES; Ka = 7.9 × 10-7

Which of the following agencies serve as sources for federal research funding?

National Science Foundation, National Institute of Health, and Department of Energy

For A --> products, time and concentration data were collected and plotted as shown here. [A] vs t, ln[A] vs t and 1/[A] vs t

Order: 1 k = 7.67*10^-3 s^-1

What is the risk in filling chemical waste containers past the recommended level?

Overflowing waste containers can lead to drips of potentially hazardous chemicals down the sides, Chemicals and their vapors need room to expand in case of increased temperatures, and when overfilled containers are moved or transported, chemicals can easily splash out

Electrolysis is the process of using electrical current to cause a nonspontaneous reaction to occur. For example, water molecules do not readily decompose into hydrogen and oxygen. However, water can be decomposed using electrolysis according to the following reaction. 2H2O ----> 2H2 + O2 Since electrolysis involves the transfer of electrons, it is classified as a type of oxidation-reduction (redox) reaction. For the reaction above, identify which atoms are oxidized and which are reduced.

Oxidized: The oxygen atom in H2O Reduced: Both hydrogen atoms in H2O

Which is the correct method for drawing liquid into a pipet?

Place a pipet bulb at the top of the pipet to draw up liquid.

Classify the actions based on how they could affect a reaction rate.

Rate increases: increase the temperature and add a catalyst Rate decreases: decreases the concentration of a reactant and decrease the surface area of a solid reactant Rate is unaffected: None

Match the following descriptions to the appropriate term.

Rate of reaction: Always has units of amount per time (e.g., M/s or M/min) Rate law: A formula that relates reactant concentration to reaction rate Rate constant: Symbolized as k and Can have different units such as M/s, s^-1, or M^-1 s^-1 depending on the reaction order

You probably saw that different sources give different regions of wavelengths associated with colors of light. This is because the colors transfer from one to the other gradually, through the mixed shades, and it is hard to establish the exact ranges. Nevertheless, it is useful to know the approximate wavelengths corresponding to the main colors of light. Match the given wavelength ranges to the colors. (Click on the wavelength, then drag and drop it into the corresponding bin.)

Red: 650-740 nm Orange: 600-640 nm Yellow: 570-600 nm Green: 510-550 nm Blue: 450-480 nm Violet; 390-420 nm

If large portions of a person\'s body are exposed to harmful chemicals, what should be done?

Remove clothing and use safety shower

Classify these compounds as strong electrolytes, weak electrolytes, or nonelectrolytes. HBr, (NH4)2S and HClO

Strong electrolyte: HBr and (NH4)2S Weak electrolyte: HClO Nonelectrolyte: None

What condition(s) must occur when a chemical reaction is at equilibrium?

The forward and reverse reactions are happening at equal rates.

Which of the following best explains why electrolyte solutions conduct electricity?

The presence of free-flowing ions

How does a buffer resist change in pH upon addition of a strong acid?

The strong acid reacts with the weak base in the buffer to form a weak acid, which produces few H ions in solution and therefore only a little change in pH.

When preparing a buret for use in lab, the buret must always be cleaned thoroughly. Prior to being filled with solution, the buret is rinsed one last time. What is the buret rinsed with, and why?

The titrant should be used to ensure that when added to the buret it will not be diluted with water.

A spectrophotometer measures the transmittance or the absorbance, or both, of a particular wavelength of light after it has passed through a liquid sample. Before the transmittance or absorbance of the sample is measured, a cuvette filled only with solvent, called the blank, is placed in the spectrophotometer and measured. Select the reason that, after the blank is measured, the cuvette must be placed in the spectrophotometer in the same orientation each time that it is used.

The transmittance of the cuvette must be measured in the same place each time.

A spectrophotometer measures the transmittance or the absorbance, or both, of a particular wavelength of light after it has passed through a liquid sample. Before the transmittance or absorbance of the sample is measured, a cuvette filled only with solvent, called the blank, is placed in the spectrophotometer. Select the following step that is NOT necessary to complete before a cuvette is placed into the spectrophotometer.

Write, in ink, either sample or blank on the side of the cuvette to keep track of them.

Consider a galvanic (voltaic) cell that has the generic metals X and Y as electrodes. If X is more reactive than Y (that is, X more readily reacts to form a cation than Y does), classify the following descriptions by whether they apply to the X or Y electrode.

X electrode: anode, anions from the salt bridge flow toward, loses mass and electrons in the wire flow away from Y electrode: cathode, electrons in the wire flow toward, cations from the salt bridge flow toward, and gains mass

Determine the oxidation number (oxidation state) of each element in the following six compounds. a) CuCO3 b) CH4 c) IF d) CH2Cl2 e) SO2 f) (NH4)2CrO4

a) Cu = +2, C = +4 and O = -2 b) C = -4 and H = +1 c) I = +1 and F = -1 d) C = 0, H = +1, and Cl = -1 e) S = +4 and O = -2 f) H = +1, N = -3, O = -2 and Cr = +6

On the weak acid/strong base titration curve below, label the following points. a) The point where the pH corresponds to a solution of the weak acid (HA) in water. b) The point where the pH corresponds to a solution of the conjugate base (A-) in water. c) The point where pH = pKa.

a) bottom titration curve b) Middle of titration curve c) bottom middle of titration curve

Indicate how the concentration of each species in the chemical equation will change to reestablish equilibrium after reactant or product is added. Rxn: 2CO + O2 = 2CO2 a) after increasing the concentration of CO b) after increasing the concentration of CO2

a) decrease, decrease and increase b) increase, increase and decrease

For the following rate law: rate = k[A]^x Determine the value of x if (a) the rate doubles when [A] is doubled. (b) no change in rate occurs when [A] is doubled.

a) x = 1 b) x = 0

In order to safely run a sample in a centrifuge, it is important to

balance the sample with a counterweight of the same mass directly across from it.

Which type of research is carried out for the purpose of gaining knowledge rather than to fulfill a specific application?

basic

If a compound is orange in color...

it absorbs blue light.

Consider this initial-rate data at a certain temperature for the reaction described by C2H5Cl ---> C2H4 and HCl Determine the value and units of the rate constant.

k = 5.95*10^-30 s^-1

A laboratory bench should always be kept free from ______

mess and clutter.

Chemicals from the laboratory should never be taken ________ the laboratory

outside

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.300 moles of a monoprotic weak acid (Ka = 4.6 × 10-5) is titrated with NaOH, what is the pH of the solution at the half-equivalence point?

pH = 4.34

If a buffer solution is 0.240 M in a weak acid (Ka = 7.6 × 10-5) and 0.510 M in its conjugate base, what is the pH?

pH = 4.447

A buffer solution is made using a weak acid, HA, with a pKa of 7.61. If the ratio of A- to HA is 1.0 × 102, what is the pH of the buffer?

pH = 9.61

Using the figure below, what are the molar absorptivities of benzoic acid at the following wavelengths? (Slopes given)

ε228 = .0893 cm^-1 ppm^-1 ε272 = .0073 cm^-1 ppm^-1