Chemistry Test Questions

Topics: Equilibrium constant, Chemical equilibrium, Partial pressure Pages: 6 (1240 words) Published: July 14, 2013
1) At equilibrium, __________.
A) all chemical reactions have ceased
B) the rate constants of the forward and reverse reactions are equal C) the rates of the forward and reverse reactions are equal D) the value of the equilibrium constant is 1
E) the limiting reagent has been consumed

2) Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

HF (s) + H2O (l) ⇌ H3O+ (aq) + F- (aq)

A) [HF][H2O] / [H3O+][F-]
B) 1 /[HF]
C) [H3O+][F-] / [HF][H2O]
D) [H3O+][F-] / [HF]
E) [F-] [H3O+]

3) The value of Keq for the equilibrium

H2 (g) + I2 (g) ⇌ 2 HI (g)

is 794 at 25 °C. At this temperature, what is the value of Keq for the equilibrium below? HI (g) ⇌ 1/2 H2 (g) + 1/2 I2 (g)

A) 0.0013 B) 28 C) 0.035 D) 397 E)1588

4) Consider the following equilibrium.

2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g)

The equilibrium cannot be established when __________ is/are placed in a 1.0-L container. A) 0.75 mol SO2(g)

B) 0.25 mol of SO2 (g) and 0.25 mol of SO3 (g)

C) 1.0 mol SO3 (g)

D) 0.50 mol O2 (g) and 0.50 mol SO3 (g)

E) 0.25 mol SO2 (g) and 0.25 mol O2 (g)

5) The equilibrium-constant expression depends on the __________ of the reaction. A) the quantities of reactants and products initially present B) stoichiometry and mechanism
C) mechanism
D) stoichiometry
E) temperature

6) At elevated temperatures, molecular hydrogen and molecular bromine react to partially form hydrogen bromide:

H2 (g) + Br2 (g) ⇌ 2HBr (g)

A mixture of 0.682 mol of H2 and 0.440 mol of Br2 is combined in a reaction vessel with a volume of 2.00 L. At equilibrium at 700 K, there are 0.566 mol of H2 present. At equilibrium, there are __________ mol of Br2 present in the reaction vessel. A) 0.440 B) 0.324 C) 0.000 D) 0.566 E) 0.232

7) At 200 °C, the equilibrium constant (Kp) for the reaction below is 2.40 × 103.

2NO (g) ⇌ N2 (g) + O2 (g)

A closed vessel is charged with 36.1 atm of NO. At equilibrium, the partial pressure of O2 is __________ atm. A) 18.1
B) 1.50 × 10-2
C) 294
D) 6.00
E) 35.7

8) The equilibrium constant for the gas phase reaction

2NH3 (g) ⇌ N2 (g) + 3H2 (g)

is Keq = 230 at 300 °C. At equilibrium, __________.
A)reactants predominate
B)products predominate
C) only products are present
D) roughly equal amounts of products and reactants are present E) only reactants are present

9) At 400 K, the equilibrium constant for the reaction

Br2 (g) + Cl2 (g) ⇌ 2BrCl (g)

is Kp = 7.0. A closed vessel at 400 K is charged with 1.00 atm of Br2 (g), 1.00 atm of Cl2 (g), and 2.00 atm of BrCl (g). Use Q to determine which of the statements below is true.

A) The equilibrium partial pressure of Br2 will be greater than 1.00 atm. B) At equilibrium, the total pressure in the vessel will be less than the initial total pressure.

C) The reaction will go to completion since there are equal amounts of Br2 and Cl2. D) The equilibrium partial pressure of BrCl (g) will be greater than 2.00 atm. E) The equilibrium partial pressures of Br2, Cl2, and BrCl will be the same as the initial value

10) The reaction below is exothermic:

2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

Le Chatelier's Principle predicts that __________ will result in an increase in the number of moles of a SO3 (g) in the reaction container. A) increasing the pressure
B) increasing the volume of the container
C) removing some oxygen
D) decreasing the pressure
E) increasing the temperature

11) In which of the following reactions would increasing pressure at constant temperature not change the concentrations of reactants and products?

A) 2N2 (g) + O2 (g) ⇌ 2N2O (g)

B) N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

C) N2 (g) + O2 (g) ⇌ 2NO (g)

D) N2O4 (g) ⇌ 2NO2 (g)

12) Consider the following reaction at equilibrium:
2NH3 (g) ⇌ N2 (g) + 3H2 (g) H°...
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