MC_Chem1B_Spring09_LecExam1 	Version A	         Name________________________

Multiple Choice
Identify the choice that best completes the statement or answers the question.

____	1.	The reaction of NO and O2 produces NO2.

2 NO(g) + O2(g) ® 2 NO2(g)

The reaction is second-order with respect to NO(g) and first-order with respect to O2(g). At a given temperature, the rate constant, k, equals 6.1 ´ 103 M-2s-1. What is the rate of reaction when the initial concentrations of NO and O2 are 0.020 M and 0.015 M, respectively?
a.	9.8 ´ 10-10 M/s	
b.	0.027 M/s	
c.	0.037 M/s	
d.	1.0 M/s	
e.	1.8 M/s	

____	2.	Which of the following statements are CORRECT?

1.	For gas phase equilibria, the partial pressures of reactants and products are equal.	
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 concentrations of reactants equals one.	

a.	1 only	
b.	2 only	
c.	3 only	
d.	1 and 2	
e.	1, 2, and 3	

____	3.	Write the expression for Kp for the reaction below.

2 Hg2O(s) ® 4 Hg(l) + O2(g)

a.	Kp = (PHg PO2 ) / (PHg2O) 	
b.	Kp =  (PHg4 PO2 ) / (P2Hg2O)  	
c.	Kp =  PHg4 PO2  	
d.	Kp =  1 / (PHg4 PO2) 	
e.	Kp =  PO2  	

____	4.	Write a balanced chemical equation which corresponds to the following equilibrium constant expression.

K = [Fe3+][OH-]3

a.	FeOH2+(s) ® Fe3+(aq) + OH-(aq)	
b.	3 Fe3+(aq) + 3 OH-(aq) ® 3 Fe(OH)3(aq)	
c.	Fe(OH)3(aq) ® Fe3+(aq) + 3 OH-(aq)	
d.	Fe(OH)3(s) ® Fe3+(aq) + 3 OH-(aq)	
e.	Fe3+(aq) + 3 OH-(aq) ® 3 Fe(OH)3(s)	

____	5.	The oxidation of sulfur dioxide produces sulfur trioxide.

2 SO2(g) + O2(g) ® 2 SO3(g)

Calculate the value of Kc, given that Kp = 2.8 ´ 102 at 999 K. (R = 0.08206 L·atm/mol·K)
a.	4.4 ´ 10-5	
b.	0.29	
c.	3.4	
d.	2.3 ´ 104	
e.	6.8 ´ 103	

____	6.	At a given temperature, an equilibrium mixture contains the following concentrations of gases: [SO3] = 0.054 M, [SO2] = 0.0047 M, and [O2] = 0.58 M. What is the equilibrium constant, Kc, for the reaction below?

2 SO3(g) ® 2 SO2(g) + O2(g)

a.	4.4 ´ 10-3	
b.	5.0 ´ 10-2	
c.	11	
d.	2.0 ´ 102	
e.	2.3 ´ 102	

____	7.	At 25 °C, only 1.9 g CaSO4 will dissolve in 2.00 L of water. What is the equilibrium constant for the reaction below?

CaSO4(s) ® Ca2+(aq) + SO42-(aq)

a.	4.9 ´ 10-5	
b.	1.9 ´ 10-4	
c.	1.4 ´ 10-2	
d.	7.0 10-3	
e.	0.90	

____	8.	At 2010 K, the equilibrium constant, Kc, for the following reaction is 4.0 ´ 10-4.

N2(g) + O2(g) ® 2 NO(g)

If the equilibrium concentrations of N2 and O2 are 0.28 mol/L and 0.38 mol/L at 2010 K, what is the equilibrium concentration of NO?
a.	1.8 ´ 10-9 M	
b.	2.1 ´ 10-5 M	
c.	4.3 ´ 10-5 M	
d.	6.5 ´ 10-3 M	
e.	6.1 ´ 10-2 M	

____	9.	Given the following chemical equilibria,

N2(g) + 3 H2(g) ® 2 NH3(g) K1
4 NH3(g) + 5 O2(g) ® 4 NO(g) + 6 H2O(g) K2
H2(g) + 1/2 O2(g) ® H2O(g) K3
 
Determine the equilibrium constant for the reaction below.

N2(g) + O2(g) ® 2 NO(g) K4

a.	K4 = K1 ´ K2 ´ K3	
b.	K4 = K1 + K2 + K3	
c.	K4 = K1 + K2 / 2 + 3K3	
d.	K4 =   3 (K1 * K2) /  2 K3  	
e.	K4 =  (K1 * K2) /  K33     	

____	10.	Given the following equilibria,

MgCO3(s) ® Mg2+(aq) + CO32-(aq) K1 = 6.8 ´ 10-6
MgF2(s) ® Mg2+(aq) + 2 F-(aq) K2 = 5.2 ´ 10-11

determine the equilibrium constant for the following reaction.

MgCO3(s) + 2 F-(aq) ® MgF2(s) + CO32-(aq) K3

a.	3.5 ´ 10-16	
b.	6.8 ´ 10-6	
c.	7.6 ´ 10-6	
d.	1.3 ´ 105	
e.	2.8 ´ 1015	

____	11.	Assume that the following endothermic chemical reaction is at equilibrium.

C(s) + H2O(g) ® H2(g) + CO(g)

Which of the following statements are CORRECT?
1.	Increasing the amount of C(s) will increase the equilibrium concentration of CO(g).	
2.	Increasing the temperature will increase the equilibrium concentration of H2(g).	
3.	Decreasing the concentration of H2O(g) will increase the equilibrium concentration of CO(g).	

a.	1 only	
b.	2 only	
c.	3 only	
d.	1 and 2	
e.	1, 2, and 3	

____	12.	In the following reaction

HCO3-(aq) + H2O(l) ® CO32-(aq) + H3O+(aq)

a.	HCO3- is an acid and H2O is its conjugate base.	
b.	HCO3- is an acid and CO32- is its conjugate base.	
c.	H3O+ is an acid and HCO3- is its conjugate base.	
d.	H2O is an acid and CO32- is its conjugate base.	
e.	H3O+ is an acid and CO32- is its conjugate base.	

____	13.	The conjugate acid of HSO4- is ____.
a.	OH-	
b.	SO42-	
c.	H2SO4	
d.	H2O	
e.	H3O+	

____	14.	Which is NOT an amphiprotic species in water?
a.	HC2O4-	
b.	CH3CO2-	
c.	HPO42-	
d.	H2PO4-	
e.	HCO3-	

____	15.	At 15 °C, the water ionization constant, Kw, is 4.5 ´ 10-15. What is the H3O+ concentration in neutral water at this temperature?
a.	2.0 ´ 10-29 M	
b.	4.5 ´ 10-15 M	
c.	6.7 ´ 10-8 M	
d.	1.5 ´ 10-7 M	
e.	2.2 M	

____	16.	What is the pH of 0.28 M HNO3(aq) at 25 °C? (Kw = 1.0 ´ 10-14)
a.	-0.55	
b.	0.28	
c.	0.55	
d.	1.27	
e.	13.45	

____	17.	An aqueous solution with a pH of 10.60 is diluted from 1.0 L to 1.5 L. What is the pH of the diluted solution?
a.	4.84	
b.	7.07	
c.	9.60	
d.	10.42	
e.	10.78	

____	18.	Assuming equal initial concentrations of the given species, which of the following is the strongest acid in an aqueous solution?
a.	benzoic acid, Ka = 6.3 ´ 10-5	
b.	formic acid, Ka = 1.8 ´ 10-4	
c.	hydrogen phosphate ion, Ka = 3.6 ´ 10-13	
d.	hydrogen sulfite ion, Ka = 6.2 ´ 10-8	
e.	nitrous acid, Ka = 4.5 ´ 10-4	

____	19.	Which salt produces a pH-neutral aqueous solution at 25 °C?
a.	KBr	
b.	NH4Cl	
c.	NaNO2	
d.	KF	
e.	FeCl3	

____	20.	Given the following equilibrium constants,

Ka (NH4+) = 5.6 ´ 10-10
Kb (NO2-) = 2.2 ´ 10-11
Kw = 1.00 ´ 10-14

determine the equilibrium constant for the reaction below at 25 °C.

NH4+(aq) + NO2-(aq) f HNO2(aq) + NH3 (aq)

a.	1.2 ´ 10-34	
b.	2.5 ´ 10-13	
c.	1.2 ´ 10-6	
d.	8.1 ´ 105	
e.	3.9 ´ 1012	

____	21.	What is the OH- concentration in 0.51 M CH3CO2-(aq)? (Kb of CH3CO2- = 5.6 ´ 10-10)
a.	2.8 ´ 10-10 M	
b.	5.6 ´ 10-10 M	
c.	5.9 ´ 10-10 M	
d.	1.7 ´ 10-5 M	
e.	1.8 ´ 10-5 M	

____	22.	What is the pH of the solution which results from mixing 35 mL of 0.50 M NH3(aq) and 35 mL of 0.50 HCl(aq) at 25 °C? (Kb for NH3 = 1.8 ´ 10-5)
a.	0.60	
b.	2.67	
c.	4.74	
d.	4.93	
e.	9.26	

____	23.	Which of the following chemical equations corresponds to Ka3 for phosphoric acid?
a.	HPO42-(aq) + H2O(l) f PO43-(aq) + H3O+(aq)	
b.	PO43-(aq) + H2O(l) f HPO42-(aq) + OH-(aq)	
c.	H3PO4(aq) + H2O(l) f H2PO4-(aq) + H3O+(aq)	
d.	H3PO4(aq) + 3 H2O(l) f PO43-(aq) + 3 H3O+(aq)	
e.	H2PO4-(aq) + H2O(l) f HPO42-(aq) + H3O+(aq)	

____	24.	All of the following species can behave as Lewis acids EXCEPT ____.
a.	F-	
b.	Al3+	
c.	SO3	
d.	Al(OH)3	
e.	CO2	

____	25.	Ozone decomposes to oxygen according to the balanced chemical equation below.

2 O3(g) ® 3 O2(g)

If the rate of disappearance of ozone is -7.2 ´ 10-4 M/s, what is the rate of formation of oxygen?
a.	4.8 ´ 10-4 M/s	
b.	7.2 ´ 10-4 M/s	
c.	1.1 ´ 10-3 M/s	
d.	1.4 ´ 10-3 M/s	
e.	2.2 ´ 10-3 M/s	

____	26.	Which of the following expressions relates the rates of reaction of NOCl(g) and Cl2(g)?

2 NOCl(g) ® 2 NO(g) + Cl2(g)

a.	 = 	
b.	-2 = 	
c.	 = 	
d.	 = 	
e.	 = 	

____	27.	What is the name given to a substance that increases the rate of a chemical reaction but is not itself consumed?
a.	reactant	
b.	product	
c.	intermediate	
d.	catalyst	
e.	element	

____	28.	What is the overall order of the reaction below

2 NO(g) + 2 H2(g) ® N2(g) + 2 H2O(g)

if it proceeds via the following rate expression?

 = k[NO]2[H2]
a.	zero-order	
b.	first-order	
c.	second-order	
d.	third-order	
e.	fourth-order	

____	29.	Given the initial rate data for the decomposition reaction,

A ® B + C

determine the rate expression for the reaction.

[A], M	-D[A]/Dt M/s	
0.110	7.81 ´ 10-3	
0.220	3.12 ´ 10-2	
0.330	7.03 ´ 10-2	

a.	 = 7.10 ´ 10-2s-1[A]	
b.	 = 0.645 M-1s-1[A]2	
c.	 = 3.63 ´ 10-2M-1s-1[A]2	
d.	 = 3.63 ´ 10-2M s-1	
e.	 = 5.87 M-2s-1[A]3	

____	30.	For the reaction A ® B, the rate law is
 = k[A].
What are the units of the rate constant where time is measured in seconds?
a.		
b.		
c.		
d.		
e.		

____	31.	The half-life of a first-order decomposition reaction is 2.36 hours. If the initial concentration of reactant is 0.52 M, what is the concentration of reactant after 752 seconds?
a.	0.046 M	
b.	0.16 M	
c.	0.26 M	
d.	0.47 M	
e.	0.49 M	

____	32.	The decomposition of formic acid follows first-order kinetics.
HCO2H(g) ® CO2(g) + H2(g)

The half-life for the reaction at 550 °C is 24 seconds. How many seconds does it take for the formic acid concentration to decrease by 75%?
a.	6.0 s	
b.	18 s	
c.	24 s	
d.	36 s	
e.	48 s	

____	33.	Molecules must overcome a barrier called the activation energy if they are to react. The highest energy point reached during the progress of a reaction is called the ____.
a.	transition state	
b.	Arrhenius state	
c.	half-life	
d.	elementary step	
e.	intermediate state	

____	34.	For a given reaction, the activation energy is 21.7 kJ/mol. If the reaction rate constant is 6.4 ´ 10-4 M-1s-1 at 25.0 °C, what is the reaction rate constant at 72.0 °C? (R = 8.314 J/K·mol)
a.	1.9 ´ 10-4 M-1s-1	
b.	6.4 ´ 10-4 M-1s-1	
c.	2.1 ´ 10-3 M-1s-1	
d.	3.6 ´ 10-3 M-1s-1	
e.	2.5 ´ 1026 M-1s-1	

MC_Chem1B_Spring09_LecExam1_A_Answer
Answer Section

MULTIPLE CHOICE

	1.	ANS:	C	PTS:	1	OBJ:	15.3 Effect of Concentration on Reaction Rate

	2.	ANS:	B	PTS:	1	OBJ:	16.2 The Equilibrium Constant and the 

	3.	ANS:	E	PTS:	1	OBJ:	16.2 The Equilibrium Constant and the 

	4.	ANS:	D	PTS:	1	OBJ:	16.2 The Equilibrium Constant and the 

	5.	ANS:	D	PTS:	1	OBJ:	16.2 The Equilibrium Constant and the 

	6.	ANS:	A	PTS:	1	OBJ:	16.3 Determining an Equilibrium Constant

	7.	ANS:	A	PTS:	1	OBJ:	16.3 Determining an Equilibrium Constant

	8.	ANS:	D	PTS:	1	OBJ:	16.4 Using Equilibrium Constant Calculations

	9.	ANS:	E	PTS:	1	

	10.	ANS:	D	PTS:	1	

	11.	ANS:	B	PTS:	1	

	12.	ANS:	B	PTS:	1	OBJ:	17.2 The Brønsted-Lowry concepts of Acids 

	13.	ANS:	C	PTS:	1	OBJ:	17.2 The Brønsted-Lowry concepts of Acids 

	14.	ANS:	B	PTS:	1	OBJ:	17.2 The Brønsted-Lowry concepts of Acids 

	15.	ANS:	C	PTS:	1	OBJ:	17.3 Water and the pH Scale

	16.	ANS:	C	PTS:	1	OBJ:	17.3 Water and the pH Scale

	17.	ANS:	D	PTS:	1	OBJ:	17.3 Water and the pH Scale

	18.	ANS:	E	PTS:	1	OBJ:	17.4 Equilibrium Constants for Acids and 

	19.	ANS:	A	PTS:	1	OBJ:	17.4 Equilibrium Constants for Acids and 

	20.	ANS:	C	PTS:	1	OBJ:	17.6 Types of Acid-Base Reactions

	21.	ANS:	D	PTS:	1	OBJ:	17.7 Calculations with Equilibrium Constants

	22.	ANS:	D	PTS:	1	OBJ:	17.7 Calculations with Equilibrium Constants

	23.	ANS:	A	PTS:	1	OBJ:	17.8 Polyprotic Acids and Bases

	24.	ANS:	A	PTS:	1	OBJ:	17.9 The Lewis Concept of Acids and Bases

	25.	ANS:	C	PTS:	1	OBJ:	15.1 Rates of Chemical Reactions

	26.	ANS:	A	PTS:	1	OBJ:	15.1 Rates of Chemical Reactions

	27.	ANS:	D	PTS:	1	OBJ:	15.2 Reaction Conditions and Rate

	28.	ANS:	D	PTS:	1	OBJ:	15.3 Effect of Concentration on Reaction Rate

	29.	ANS:	B	PTS:	1	OBJ:	15.3 Effect of Concentration on Reaction Rate

	30.	ANS:	A	PTS:	1	OBJ:	15.3 Effect of Concentration on Reaction Rate

	31.	ANS:	E	PTS:	1	

	32.	ANS:	E	PTS:	1	

	33.	ANS:	A	PTS:	1	OBJ:	15.5 A Microscopic View of Reaction Rates

	34.	ANS:	C	PTS:	1	OBJ:	15.5 A Microscopic View of Reaction Rates