Chem Exam 3 - Chapter 15

Which one of the following will change the value of an equilibrium constant? A) changing temperature B) adding other substances that do not react with any of the species involved in the equilibrium C) varying the initial concentrations of reactants D) varying the initial concentrations of products E) changing the volume of the reaction vessel

A) changing temperature

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 in the reaction container. A) increasing the pressure B) decreasing the pressure C) increasing the temperature D) removing some oxygen E) increasing the volume of the container

A) increasing the pressure

For the endothermic reaction CaCO3 (s) -----> CaO (s) + CO2 (g) Le Chatelier's principle predicts that __________ will result in an increase in the number of moles of CO2. A) increasing the temperature B) decreasing the temperature C) increasing the pressure D) removing some of the E) none of the above

A) increasing the temperature

Consider the following reaction at equilibrium: 2NH3 (g)------> N2 (g) + 3 H2 (g) Le Chatelier's principle predicts that the moles of H2 in the reaction container will increase with __________. A) some removal of from the reaction vessel (V and T constant) B) a decrease in the total pressure (T constant) C) addition of some to the reaction vessel (V and T constant) D) a decrease in the total volume of the reaction vessel (T constant) E) an increase in total pressure by the addition of helium gas (V and T constant)

B) a decrease in the total pressure (T constant)

The equilibrium constant for the gas phase reaction N2 (g) + 3 H2 (g) -------> 2 NH3 (g) is k=4.34x10-3 at 300 °C. At equilibrium, __________. A) products predominate B) reactants predominate C) roughly equal amounts of products and reactants are present D) only products are present E) only reactants are present

B) reactants predominate

At equilibrium, __________. A) all chemical reactions have ceased B) the rates of the forward and reverse reactions are equal C) the rate constants of the forward and reverse reactions are equal D) the value of the equilibrium constant is 1 E) the limiting reagent has been consumed

B) the rates of the forward and reverse reactions are equal

In an exothermic equilibrium reaction, increasing the reaction temperature favors the formation of _______.

Reactants

The effect of a catalyst on an equilibrium is to __________. A) increase the rate of the forward reaction only B) increase the equilibrium constant so that products are favored C) slow the reverse reaction only D) increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture E) shift the equilibrium to the right

D) increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture

For an exothermic reaction, increasing the reaction temperature results in a(an) __________ in the equilibrium constant K.

Decrease

Which of the following statements is true? A) Q does not change with temperature. B) K does not change with temperature, whereas Q is temperature dependent. C) K does not depend on the concentrations or partial pressures of reaction components. D) Q does not depend on the concentrations or partial pressures of reaction components. E) Q is the same as K when a reaction is at equilibrium.

E) Q is the same as K when a reaction is at equilibrium.

How is the reaction quotient used to determine whether a system is at equilibrium? A) The reaction quotient must be satisfied for equilibrium to be achieved. B) At equilibrium, the reaction quotient is undefined. C) The reaction is at equilibrium when Q<K. D) The reaction is at equilibrium when Q>K. E) The reaction is at equilibrium when Q=K.

E) The reaction is at equilibrium when Q=K.

If a reaction is endothermic, __________ the reaction temperature results in an increase in K.

Increase

The equilibrium-constant expression for a reaction written in one direction is the __________ of the one for the reaction written for the reverse direction.

Inverse

Pure __________ and pure __________ are excluded from equilibrium-constant expressions

Liquids, solids

If the value for the equilibrium constant is much greater than 1, then the equilibrium mixture contains mostly __________.

Products

If the reaction quotient Q for a reaction is greater than the value of the equilibrium constant K for that reaction at a given temperature, __________ must be converted to __________ for the system to reach equilibrium.

Products, reactants

If the reaction quotient Q for a reaction is less than the value of the equilibrium constant K for that reaction at a given temperature, __________ must be converted to __________ for the system to reach equilibrium.

Reactants, products