The forward and reverse rates reaction are equal

Chemistry 112, Fall 2006, Section 1 (Garman and Heuck) Exam 2a (100 points)
9 Nov 2006

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Use the exam as scratch paper. We will not grade anything on the exam itself. Turn in both the exam and bubble sheet when you are done. Good luck!

c) Arrhenius acids.

d) Brønsted-Lowry acids.
e) strong electrolytes.

3. (3 points) For a reversible reaction at the equilibrium
a) The concentration of reactants equals the concentration of products. b) The forward and reverse reactions still occur.

c) The rates of the forward and reverse reactions are equal to zero. d) The value of Q = K only for reactions in the gas phase.

a) OH-	2- b) SO4	c) H2SO4	d) H2O	e) H3O+

Chem 112, Fall 06, Section 1 Exam 2a

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d) increase the concentration of the three compounds. e) none of the above.

10. (4 points) At 50 °C, the water ionization constant, Kw, is 5.5 × 10-14. What is the H3O+ concentration in neutral water at this temperature?

Chem 112, Fall 06, Section 1 Exam 2a

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c) HCO2-(aq) + H2O(l) � HCO2H(aq) + OH-(aq)

d) HCO2-(aq) + H3O+(aq) � HCO2H (aq) + H2O(l)

c) 0.10 M KCH3CO2 + 0.05 M CH3CO2H

d) 0.10 M NaCl + 0.05 M HCl

b) formic acid, Ka = 1.8 × 10-4

c) benzoic acid, Ka = 6.3 × 10-5

a) 1.3 × 10-5 b) 7.8 × 10-10 c) 1.3 ×10-19 d) -9.11 e) 9.11

17. (4 points) Which salt forms a 0.10 M aqueous solution with the lowest pH?

	b) NaCl	c) NaF	d) NH4Cl

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18. (6 points) What is the H3O+ concentration in 0.45 M HCN(aq)? (Ka of HCN = 4.0 × 10-10)

1. The pH will decrease.

2. The concentration of NH3 will increase. 3. The concentration of H3O+ will increase.			d) 1 and 3
	b) 2 only	c) 3 only	d) 1 and 3

2. For a chemical system at equilibrium, the forward and reverse rates of reaction are equal.

3. For an aqueous chemical system at equilibrium, the concentrations of products divided by the

	b) 1 and 2	c) 2 only	d) 3 only	e) 1, 2, and 3

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22. (4 points) Write a balanced chemical equation which corresponds to the following equilibrium constant

a)	K	c	K p = ( RT )				2
b)
c)	K	c	= ( RT			)	K
d)	K	c	= ( RT			)	K
d)	K = RT c ⎛ ⎜⎝K p							2
e)	K	c =		⎛	K	p		2
	K	c =		⎜⎝	RT			2

b) [SO3] will decrease because Q < K.

c) [SO3] will increase because Q < K.

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25. (6 points) The equilibrium constant, Kc, for the following reaction is 1.0 × 10-5 at 1500 K.

Chem 112, Fall 06, Section 1 Exam 2a

				e) 2.5 × 1012
a) 4.0 × 10-13		c) 7.8 × 10-7	d) 1.3 × 10-8	e) 2.5 × 1012

Please sign the following statement at the completion of the exam:

I did not cheat on this exam. _______________________________(name)

1.008

4.003

4

10

6.939

10.81

12.01

14.01

16.00

19.00

12

18

Ca S 40.08 44.				Mn F 54.94 55
Ba L 137.3 13	40 Zr	41 Nb
	91 91.22 72			75 76 Re O
	104	181.0 105			8 109
	c Un			(262) (26	no Un
				Kw

			e]/[acid
			e]/[acid

ln(k2/k1) = (-Ea/R)(1/T2-1/T1)

T (°

R = 8.31x10-3 kJ/(mol K) =

= 0.0821 (L atm)/(mol K) 22.99 24.31 32.07 35.45 39.95

Rb Ag Te I Xe

85.47 107.9 127.6 126.9 131.3

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