CEM 142

Exam 2 Study Stuff WN 06

Here is Exam 2 from WN 05

Chapter 15

Vocabulary Checklist:

equilibrium constant, Lechatlier's principle, reaction quotient

Concept checklist:

1. Correlate reaction rates of opposing reactions and the equilibrium constant of said system.
2. Write the equilibrium constant expression of any reaction and use it in calculations regarding concentrations of solutions.
3. Explain Lechatlier's principle and understand and predict examples of it.
4. Define reaction quotient and how it related to predicting chemical processes.

Problems: Chapter 15: 1,7,9,11,15,17,19,25,27,29,31,35,43,45,49,53,59,65,74

Some other 'hints': 

Last years chpt 15 Questions (No guarantees)

1. (16) For the reaction

1 Ni(s) + 4 CO(g) « 1 Ni(CO)4(g) DHrxn < 0

which way will the equilibrium shift in response to the following changes in conditions. Explain why. Use small words. If unaffected, explain why.

a. increase in T       b. increase in reaction V  c. addition of Ni(s)  d. removal of Ni(CO)4(g)

2. (12) Consider a system that originally has equimolar amounts of SO2 and O2 (only) at 1030 ºC.  You read somewhere that the reaction 2 SO2(g) + 1 O2(g) D 2 SO3(g) has a Kc (not Keq) of 1.98 at 1030ºC. Without doing any calculations, indicate whether each of the following statements is true or false as the system eeks towards equilibrium and explain in detail why it is true or false.
            a. The total pressure of the mixture increases.
            b. The number of moles of SO3(g) at equilibrium is twice the number of moles of O2(g) initially.
            c. The equilibrium mixture no longer has equal molar ratios of SO2 and O2.
3. (12) Into a container, 1.200 atm of BrCl(g) is introduced and based on the following equilibrium:
1 Br2(g) + 1 Cl2(g) D 2 BrCl(g) something happens. After the system attains equilibrium, the pressure of Cl2(g) is .33 atm. What is the value of Keq for this reaction?
4. (10) Explain how each of the following affects the vapor pressure of a liquid. If there is a mathematical relationship, explain (as best you can) what that relationship is.
            a. surface area            b. intermolecular attractive forces            c. temperature

Chapter 16:

Vocabulary Checklist:

Arrehenius acid and base ; Bronstad-Lowry acid and base ; conjugate acid / base ; autoionization ; hydrolysis

Concept checklist:

1. Given an acid or base, write the conjugate and indicate whether it is strong or weak.
2. Understand what autoionization means and what impact it has on solutions.
3. Define polyprotic acid and perform salient calculations.
4. Understand and describe hydrolysis.
5. Define common ion effect and understand how it effects solutions. Do calculations.
6. Describe Lewis acid base theory

Problems: Chapter 16: 1,5,13,15,17,19,27,31,35,41,45,49,63,65,67,77,89,107,110

Some other 'hints':

~On the OTE you will be given the value of Kw.

Pseudo-sample questions:

1. Which is a stronger acid, the conjugate acid of XXX or the conjugate acid of YYY. Explain why.

2. What is the pH of a XXX M solution of base BB knowing that Ka for the conjugate acid is YYY.

3. Explain how XXX is a Arrehenius acid, a bronsted-Lowry acid and a Lewis acid.

LAST YEARS Chpt 16 exam QUESTIONS: (no guarantees are made as to how close this years will match)

1. (14) I take 2.00 g of tartaric acid (a diprotic acid, H2C4H4O6) into some water and dilute the solution to exactly 150.0 mL. Ka1 = 1.0 x 10-3 , Ka2 =4.6 x 10-5. What is the concentration of every ion in the solution. When I say EVERY, I mean every. (hint: there are more than 3 ions in solution, less than 7)
2. (8) HOI and HOBr are acids that are not really strong, nor really weak. Which is a stronger base, OI- or OBr-? Why? The explanation is worth 6 of the possible points.
3. (10) I take a beaker of water and add some NaMnO4. Is the resultant solution acidic, basic, or neutral? Why? I add some DI H2O to the solution. Does the pH increase, decrease or stay the same. Why?
4. (8) There are three different ways of defining what a 'base' is. Give me two such definitions and a DETAILED example of each. A well labeled chemical equation would really help.

Chapter 17:

Vocabulary Checklist:

buffer ; solubility product constant ; common ion effect ; complex ions ; qualitative analysis

Concept checklist:

1. Understand the purpose of a buffer and explain how to make one
2. Define solubility product constant and know how to do calculations with it.
3. Define complex ion and know how to do calculations with Kf.
4. Describe qualitative analysis in simple terms.

Problems:
Chapter 17: 1,6,11,13,25,31,37,47,49,63,69,78,98

Some other 'hints':

On the exam you will be given the value of Kw as well as the buffer equation (pHbuffer =pKa....)

Previous chpt 17 exam questions: (no guarantees about relationship to this years, but a good study guide)

1. (14) I have a solution that is 0.100 M in each of the following solutions: NaC2H3O2, NH4Cl, AgNO3.
a) Are there any reactions? If yes, what are they?
b) What are the identities of all ions in solution. Give estimations of concentrations of each. 'About 0.100 M' , 'really small', or 'zero' are the kind of answers I am looking for.
c) Do you expect the solution to acidic or basic, why?
2. (12) I have 100.00 mL of a 0.193 M HF Solution (Ka = 6.8 x 10-4) in a beaker. I begin to titrate it with a 0.234 M KOH solution.
a) At what V is the equivalence point?
b) calculate the pH at this point.
c) add 10.0 mL more of KOH past the equivalence point. What is the pH here?
3. (12) I take a sample of solid sludge I picked up on the street. It completely dissolves in pure water. On addition of HCl, a precipitate forms. I filter off said precipitate and adjust the pH to about 1 and then add H2S. A precipitate again forms. I filter that one off, and then adjust the solution to a pH of 8 and bubble more H2S into it. No precipitate forms this time. No precipitate forms upon addition of (NH4)2HPO4. Consider these possible things that were in the sample of sludge: Pb(NO3)2, HgO, ZnSO4, Cd(NO3)2, Na2SO4.
a) Which compounds are definitely present?
b) Which compounds are definitely NOT present?
c) Which compounds MIGHT be present?
4. (12) The Hydrogen Phthalate ion, HC8H5O4- is a weak monoprotic acid. When 525 mg of Potassium hydrogen phthalate is dissolved in enough water to make 250.0 mL of solution, the pH is 4.24. Calculate Kb for the Phthalate ion (C8H5O4-2)

Last edited 6 Jan 06