Q: If $Q < K$ for a reaction mixture, what will happen as the system moves toward equilibrium?

The reaction will shift toward products.

Q: Which of the following statements about homogeneous and heterogeneous equilibria is correct?

In heterogeneous equilibria, the concentration of pure solids and liquids is taken as 1.

Question 1

Which of the following best describes a system at chemical equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $\ce{N2(g) + 3H2(g) <=> 2NH3(g)}$, the equilibrium constant expression in terms of concentrations is:

Accepted Answer

$K_c = \frac{[\ce{NH3}]^2}{[\ce{N2}][\ce{H2}]^3}$

Question 3

If the equilibrium constant $K$ for a reaction is much greater than 1, what does this indicate about the reaction at equilibrium?

Accepted Answer

Products predominate at equilibrium.

Question 4

For the reaction $\ce{2SO2(g) + O2(g) <=> 2SO3(g)}$, if the equilibrium constant $K_c$ is 4.0 at a certain temperature, what is the value of $K_c$ for the reverse reaction?

Accepted Answer

$K_c = 0.25$

Question 5

A reaction has an equilibrium constant $K_c = 10$ at a certain temperature. If the equation is doubled, what is the new equilibrium constant?

Accepted Answer

$K_c = 100$

Question 6

Which of the following changes will shift the equilibrium of the reaction $\ce{N2(g) + 3H2(g) <=> 2NH3(g)}$ to the right (toward more ammonia) according to Le Châtelier’s Principle?

Accepted Answer

Increasing the pressure.

Question 7

For the reaction $\ce{CaCO3(s) <=> CaO(s) + CO2(g)}$, which of the following is included in the equilibrium constant expression?

Accepted Answer

$[\ce{CO2}]$

Question 8

A catalyst is added to a system at equilibrium. What is the effect on the equilibrium position and the rate at which equilibrium is achieved?

Accepted Answer

The equilibrium position does not change, but equilibrium is reached faster.

Question 9

Given the reaction $\ce{A(g) <=> 2B(g)}$ with $K_p = 0.50$ at a certain temperature, what is the value of $K_c$ if the total pressure is 1.0 atm and the temperature is 298 K? (Assume ideal gas behavior.)

Accepted Answer

$K_c = 0.50 	imes (RT)^{-1}$

Question 10

A mixture initially contains 1.0 M $\ce{H2}$ and 2.0 M $\ce{I2}$. At equilibrium, $\ce{HI}$ is found to be 1.87 M. What is the equilibrium concentration of $\ce{H2}$?

Accepted Answer

0.065 M

Question 11

If $Q < K$ for a reaction mixture, what will happen as the system moves toward equilibrium?

Accepted Answer

The reaction will shift toward products.

Question 12

Which of the following statements about homogeneous and heterogeneous equilibria is correct?

Accepted Answer

In heterogeneous equilibria, the concentration of pure solids and liquids is taken as 1.

Question 13

For the reaction $\ce{2NO2(g) <=> N2O4(g)}$, how will increasing the volume of the container affect the equilibrium?

Accepted Answer

It will shift toward the side with more moles of gas.

Question 14

Which of the following is true about the reaction quotient $Q$?

Accepted Answer

$Q$ is calculated using current concentrations, not necessarily equilibrium concentrations.

Question 15

A closed system at equilibrium is disturbed by adding more reactant. According to Le Châtelier’s Principle, what will happen?

Accepted Answer

The system will produce more product to counteract the change.

Question 16

Which of the following best explains why the equilibrium constant changes with temperature?

Accepted Answer

Because the relative energies of reactants and products change with temperature.

Question 17

For the reaction $\ce{A <=> B}$, if the equilibrium constant is $K = 0.01$, which statement is true?

Accepted Answer

At equilibrium, [A] is much greater than [B].

Question 18

Which of the following is a correct statement about consecutive equilibria?

Accepted Answer

The equilibrium constant for the overall reaction is the product of the individual constants.

Question 19

A reaction is endothermic. What will happen to the equilibrium position if the temperature is increased?

Accepted Answer

The equilibrium will shift toward products.

Question 20

Which of the following is NOT a characteristic of a system at equilibrium?

Accepted Answer

The system is static and no reactions occur.

Chemical Equilibrium: Principles and Applications

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