Chemistry 124 Spring 2016 Name___________________________________

Exam 2 VERSION 1 - make sure you mark your version number in the TN box on the side of the scantron sheet

There are 53 questions on the exam - each question is worth 2 points - the total for the exam is 106 graded out of 100 (6bonus points)

1) Given the following balanced equation, determine the rate of reaction with respect to [NOCl].

2 NO(g) + Cl2(g) → 2 NOCl(g)

A) Rate = - 12

∆[NO]∆t

B) Rate = - 12

∆[NOCl]∆t

C) Rate = + 12

∆[NOCl]∆t

D) Rate = - 2 ∆[NOCl]∆t

E) It is not possible to determine without more information.

2) Using the equation below, if the rate of Cl2 loss is 4.84 × 10-2 M/s, what is the rate of formation of NOCl?

2 NO(g) + Cl2(g) → 2 NOCl(g)

A) 9.68 × 10-2 M/sB) 4.84 × 10-2 M/sC) 1.45 × 10-1 M/sD) 2.42 × 10-2 M/sE) 1.61 × 10-2 M/s

3) For a first order reaction having only one reactant which of the following is correct?A) The rate of the reaction is proportional to the square root of the concentration of the reactant.B) The rate of the reaction is proportional to the square of the concentration of the reactant.C) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant.D) The rate of the reaction is not proportional to the concentration of the reactant.E) The rate of the reaction is directly proportional to the concentration of the reactant.

4) For a second order reaction having only one reactant which of the following is correct?A) The rate of the reaction is proportional to the square root of the concentration of the reactant.B) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant.C) The rate of the reaction is not proportional to the concentration of the reactant.D) The rate of the reaction is directly proportional to the concentration of the reactant.E) The rate of the reaction is proportional to the square of the concentration of the reactant.

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5) What is the overall order of the following reaction, given the rate law?

NO(g) + O3(g) → NO2(g) + O2(g) Rate = k[NO][O3]

A) 1 12

order B) 3rd order C) 1st order D) 2nd order E) 0th order

6) Given the following rate law, how does the rate of reaction change if the concentration of Y is doubled?

Rate = k [X][Y]2

A) The rate of reaction will decrease by a factor of 2.B) The rate of reaction will increase by a factor of 2.C) The rate of reaction will increase by a factor of 4.D) The rate of reaction will increase by a factor of 5.E) The rate of reaction will remain unchanged.

7) Determine the rate law for the following reaction using the data provided.

S2O82⁻(aq) + 3 I⁻(aq) → 2 SO42⁻(g) + I3⁻(aq)

[S2O82⁻]i (M) [I⁻]i (M) Initial Rate (M-1s-1)0.30 0.42 4.540.44 0.42 6.650.44 0.21 3.33

A) Rate = [S2O82⁻][I⁻]2

B) Rate = [S2O82⁻][I⁻]

C) Rate = [S2O82⁻][I⁻]1/2

D) Rate =[S2O82⁻]2[I⁻]

E) Rate = [S2O82⁻]2[I⁻]2

8) Which of the following represents the integrated rate law for a first-order reaction?A) [A]t - [A]o = - kt

B) 1[A]t

- 1[A]o

= kt

C) lnk2k1

= EaR

1T

+ lnA

D) k = Ae(-Ea/RT)

E) ln[A]t[A]o

= - kt

9) How many half-lives are required for the concentration of reactant to decrease to 25% of its original value?A) 2 B) 1.5 C) 2.5 D) 1 E) 3

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10) Given the following proposed mechanism, predict the rate law for the overall reaction.

2NO2 + Cl2 → 2NO2Cl (overall reaction)

MechanismNO2 + Cl2 → NO2Cl + Cl slowNO2 + Cl → NO2Cl fast

A) Rate = k[NO2][Cl2]B) Rate = k[NO2Cl][Cl]

C) Rate = k[NO2]2[Cl2]

D) Rate = k[NO2Cl]2

E) Rate = k[NO2][Cl]

11) What data should be plotted to show that experimental concentration data fits a zeroth-order reaction?A) 1/[reactant] vs. timeB) [reactant] vs. timeC) ln[reactant] vs. timeD) ln(k) vs. EaE) ln(k) vs. 1/T

12) What data should be plotted to show that experimental concentration data fits a first-order reaction?A) ln(k) vs. EaB) [reactant] vs. timeC) ln[reactant] vs. timeD) 1/[reactant] vs. timeE) ln(k) vs. 1/T

13) Which of the following conditions must be met for a chemical reaction to happen in gas phase?A) Molecules must collide with proper orientation.B) Molecules must collide.C) Molecules must have the activation energy.D) All of the above conditions must be met.

14) Which is the definition of Lewis base?A) a proton donor B) proton acceptorC) an electron pair donor D) an electron pair acceptor

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15) Which rate law is consistent with the proposed mechanism for the reaction?

NO2(g) + CO(g) → NO2(g) + CO2(g) Mechanism:2 NO2(g) → NO3(g) + NO(g) (fast)NO3(g) + CO(g) → NO2(g) + CO2(g) (slow)

A) Rate = k[NO2][CO] B) Rate = k[NO3][CO]

C) Rate = k[NO2]2 D) Rate = k[NO2]2[CO]

16) The decomposition of dinitrogen pentoxide is described by the chemical equation:

2 N2O5(g) → 4 NO2(g) + O2(g)

If the rate of disappearance of N2O5 is equal to 1.60 mol/min at a particular moment, what is the rate ofappearance of NO2 at that moment?A) 3.20 mol/min B) 1.60 mol/min C) 0.800 mol/min D) 6.40 mol/min

17) Which of the following statements is false?A) When K >> 1, the forward reaction is favored and essentially goes to completion.B) When K << 1, the reverse reaction is favored and the forward reaction does not proceed to a greatextent.

C) K >> 1 implies that the reaction is very fast at producing products.D) When K ≈ 1, neither the forward or reverse reaction is strongly favored, and about the same amount ofreactants and products exist at equilibrium.

E) None of the above

18) Express the rate law for the following reaction.

2 CH3Cl(g) + Cl2(g) ⇌ 2 CH2Cl2(g) + H2(g)

A) K = [CH3Cl][Cl2][CH2Cl2][H2]

B) K = [CH3Cl]1/2[Cl2]

[CH2Cl2]1/2[H2]

C) K = [CH2Cl2][H2][CH3Cl][Cl2]

D) K = [CH3Cl]2[Cl2]

[CH2Cl2]2[H2]

E) cannot be determined from the information given

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19) Express the equilibrium constant for the following reaction.

PCl5(g) ⇌ PCl3(g) + Cl2(g)

A) K = [PCl5]

[PCl3][Cl2]

B) K = [PCl3][Cl2][PCl5]

C) K = [PCl5]1/2

[PCl3]1/2[Cl2]1/2

D) K = [PCl3][Cl]2

[PCl5]

E) cannot be determined from the information given

20) What is △n for the following equation in relating Kc to Kp?

N2(g) + 3 H2(g) ⇌ 2 NH3(g)

A) -4 B) 4 C) 2 D) 1 E) -2

21) In which of the following reactions will Kc = Kp?A) N2O4(g) ⇌ 2NO2(g)B) H2(g) + I2(g) ⇌ 2 HI(g)C) N2(g) + 3 H2(g) ⇌ 2 NH3(g)D) CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g)E) CO(g) + 2 H2(g) ⇌ CH3OH(g)

22) Determine the value of Kc for the following reaction if the equilibrium concentrations are as follows: [H2]eq= 0.14 M, [I2]eq = 0.39 M, [HI]eq = 1.6 M.

H2(g) + I2(g) ⇌ 2 HI(g)

A) 47 B) 2.1 × 10-2 C) 3.4 × 10-2 D) 8.7 × 10-2 E) 29

23) Consider the following reaction at equilibrium. What effect will adding more H2S have on the system?

2 H2S(g) + 3 O2(g) ⇌ 2 H2O(g) + 2 SO2(g)

A) The equilibrium constant will decrease.B) The equilibrium constant will increase.C) The reaction will shift in the direction of products.D) The reaction will shift to the left.E) No change will be observed.

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24) Consider the following reaction at equilibrium. What effect will increasing the pressure of the reactionmixture have on the system?

2 H2S(g) + 3 O2(g) ⇌ 2 H2O(g) + 2 SO2(g)

A) No effect will be observed.B) The equilibrium constant will decrease.C) The reaction will shift to the right in the direction of products.D) The reaction will shift to the left in the direction of reactants.E) The equilibrium constant will increase.

25) Which is true for a chemical reaction at equilibrium?A) The molecules have stopped moving.B) There are no observable changes, but the forward and reverse reactions continue.C) The reaction proceeds in forward direction.D) The reaction has stopped.

26) What will happen to the following reaction at equilibrium if the pressure is increased?

N2(g) + 3H2(g) ⇌ 2NH3(g)

A) Less NH3 will be produced. B) More NH3 will be produced.C) There will be no change in concentrations. D) More N2 and H2 will be produced.

27) Consider the following reaction at equilibrium. What effect will increasing the temperature have on thesystem?

Fe3O4(s) + CO(g) + heat ⇌ 3 FeO(s) + CO2(g)

A) The reaction will shift to the left in the direction of reactants.B) The equilibrium constant will increase.C) The reaction will shift to the right in the direction of products.D) No effect will be observed.E) The equilibrium constant will decrease.

28) The equilibrium constant is equal to 5.00 at 1300 K for the reaction:

2 SO2(g) + O2(g) ⇌ 2 SO3(g).

If initial concentrations are [SO2] = 6.00 M, [O2] = 0.45 M, and [SO3] = 9.00 M, the system isA) not at equilibrium and will shift to the left to achieve an equilibrium state.B) at equilibrium.C) not at equilibrium and will remain in an unequilibrated state.D) not at equilibrium and will shift to the right to achieve an equilibrium state.

29) Which of the following is a Br∅nsted-Lowry acid?A) NH4+ B) NH3 C) Br2 D) CH4 E) NH2-

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30) Which of the following is a Br∅nsted-Lowry base?A) CH4B) Cl2C) NH3D) HCNE) None of the above are Br∅nsted-Lowry bases.

31) What is the conjugate acid of HCO3⁻?

A) H3O+ B) H2O C) H2CO3 D) CO32- E) OH⁻

32) Identify the weak diprotic acid.A) H3PO4 B) HClO4 C) HNO3 D) H2SO3 E) H2SO4

33) Identify the triprotic acid.A) HClO4 B) H2SO3 C) H2SO4 D) HNO3 E) H3PO4

34) Which of the following is true?A) An acidic solution has [H3O⁺] > [OH⁻]B) A neutral solution does not contain any H3O+ or OH-

C) A neutral solution contains [H2O] = [H3O⁺]D) A basic solution does not contain H3O+

E) None of the above are true.

35) What is the concentration of hydroxide ions in pure water at 30.0∘C, if Kw at this temperature is

1.47 × 10-14?

A) 1.47 × 10-7 MB) 1.21 × 10-7 MC) 1.30 × 10-7 MD) 1.00 × 10-7 ME) 8.93 × 10-8 M

36) Calculate the pH of a solution that contains 3.9 × 10-4 M H3O⁺ at 25°C.A) 0.59 B) 4.59 C) 3.41 D) 10.59 E) 9.41

37) Calculate the hydronium ion concentration in an aqueous solution with a pH of 9.85 at 25°C.A) 6.5 × 10-5 MB) 1.4 × 10-10 MC) 7.1 × 10-5 MD) 8.7 × 10-10 ME) 4.2 × 10-10 M

38) Determine the pH of a 0.023 M HNO3 solution.A) 2.30 B) 3.68 C) 1.64 D) 12.36 E) 2.49

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39) Calculate the pH of a solution that contains 7.8 × 10-6 M OH⁻ at 25°C.A) 9.64 B) 1.28 C) 5.11 D) 8.89 E) 12.72

40) Which of the following acids is the strongest? The acid is followed by its Ka value.

A) HNO2, 4.6 × 10-4

B) HF, 3.5 × 10-4

C) HCHO2, 1.8 × 10-4

D) HClO2, 1.1 × 10-2

E) HCN, 4.9 × 10-10

41) Determine the [OH⁻] concentration in a 0.235 M NaOH solution.A) 4.25 × 10-14 MB) 0.470 MC) 0.198 MD) 0.235 ME) 2.13 × 10-14 M

42) Which of the following is a Lewis base?A) AlF3B) H2OC) C5H12D) SiF4E) None of the above are Lewis bases.

43) Calculate the hydroxide ion concentration in an aqueous solution that contains 3.50 × 10-4 M in hydroniumion.A) 2.86 × 10-10 M B) 3.50 × 10-11 M C) 2.86 × 10-11 M D) 2.86 × 10-3 M

44) Calculate the molarity of hydroxide ion in an aqueous solution that has a pOH of 5.00.A) 5.0 × 10-14 B) 9.0 × 10-14 C) 9.00 D) 1.0 × 10-9 E) 1.0 × 10-5

45) Which pair is not a conjugate acid-base pair?A) H3O+; H2O B) HNO2; NO2-

C) H2SO4; H2SO3 D) (CH3)3N; (CH3)3NH+

46) The pOH of pure water at 40oC is 6.8. What is the hydronium ion concentration in pure water [H3O+] at thistemperature?A) 1.0 × 10-7 B) 6.3 × 10-8 C) 1.6 × 10-7 D) 1 × 10-14

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47) Which of the following represents the equation for a first-order half-life?

A) t 1/2 = 0.693k

B) t 1/2 = k[A]o

C) t 1/2 = 1k[A]o

D) t 1/2 = [A]o2k

E) t 1/2 = 2k[A]o

48) The graph represents the first-order decomposition of N2O5(g) to form NO2(g) and O2(g). N2O5(g) → 2NO2(g) +1/2O2(g)

What will be the N2O5 concentration after 7.0 hours?

A) 0.10 mol/L B) 0.18 mol/L C) 0.14 mol/L D) 0.70 mol/L

49) The equilibrium constant is given for one of the reactions below. Determine the value of the missingequilibrium constant.

2 HD(g) ⇌ H2(g) + D2(g) Kc = 0.282 H2(g) + 2 D2(g) ⇌ 4 HD(g) Kc = ?

A) 7.8 × 10-2 B) 13 C) 1.9 D) 3.6 E) 0.53

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50) Consider the following reaction:

NO(g) + SO3(g) ⇌ NO2(g) + SO2(g)

A reaction mixture initially contains 0.86 atm NO and 0.55 atm SO3. Determine the equilibrium pressure ofNO if the concentration of NO2 at this temperature is 0.118.A) 0.86 atm B) 0.118 atm C) 0.432 atm D) 0.55 atm E) 0.31 atm

51) Which statement is true for the following reaction at equilibrium at 25 C?

H2(g) + Br2(g) ⇌ HBr(g); K = 1.9 × 1019

A) The rate of the reaction is very slow. B) Concentration of H2 and Br2 are high.C) The reverse reaction does not happen. D) Concentration of HBr is high.

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Answer KeyTestname: CHEM124EXAM2V1_2016

1) C2) A3) E4) E5) D6) C7) B8) E9) A10) A11) B12) C13) D14) C15) C16) A17) C18) E19) B20) E21) B22) A23) C24) C25) B26) B27) C28) B29) A30) C31) C32) D33) E34) A35) B36) C37) B38) C39) D40) D41) D42) B43) C44) E45) C46) B47) A48) B49) B

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Answer KeyTestname: CHEM124EXAM2V1_2016

50) E51) D

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