Question 1

Which of the following best describes Le Châtelier’s principle?

Accepted Answer

A system at equilibrium will shift to minimize the effect of a disturbance.

Question 2

Consider the equilibrium: $$\mathrm{Fe$$^{3+}$$(aq) + SCN^-(aq) \rightleftharpoons $$FeSCN^{2+}$$(aq)}. If $$more $$\mathrm{SCN^-} is $$added to the system at equilibrium, what will happen to the concentration of $$\mathrm{$$FeSCN^{2+}$$}$$?

Accepted Answer

It will increase.

Question 3

A reaction at equilibrium is represented by $$\mathrm{2CO_2(g) \rightleftharpoons 2CO(g) + O_2$(g)}. $$What will happen if $$\mathrm{CO(g)} is $$removed from the system?

Accepted Answer

The equilibrium will shift to the right, producing more $$\mathrm{CO}$$ and $$\mathrm{O_2$}.$$

Question 4

Which of the following changes will NOT affect the equilibrium position of a chemical system?

Accepted Answer

Adding a catalyst.

Question 5

For the endothermic reaction $$\mathrm{N_2O_4(g) + energy \rightleftharpoons 2NO_2(g)}$$, what will happen if the temperature is increased?

Accepted Answer

The equilibrium will shift to the right, producing more $$\mathrm{NO_2$}.$$

Question 6

A sealed container holds the equilibrium $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}. If $$the volume of the container is halved, what is the predicted shift in equilibrium?

Accepted Answer

Shift to the right, producing more $$\mathrm{NH_3$}.$$

Question 7

Which of the following best explains why adding an inert gas to a reaction vessel at constant volume does NOT shift the equilibrium?

Accepted Answer

The partial pressures of the reactants and products do not change.

Question 8

In the industrial production of nitric acid, $$\mathrm{3NO_2(g) + H_2O(l) \rightleftharpoons 2HNO_3(aq) + NO(g)}$$, why is nitric oxide gas continuously removed?

Accepted Answer

To shift the equilibrium to the right and increase $$\mathrm{$$HNO_3$$}$$ yield.

Question 9

Which statement about catalysts and equilibrium is correct?

Accepted Answer

A catalyst increases the rate at which equilibrium is reached but does not change the equilibrium position.

Question 10

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g) + energy}$$, what will happen if the temperature is decreased?

Accepted Answer

The equilibrium will shift to the right, producing more $$\mathrm{SO_3$}.$$

Question 11

A student adds more solid $$\mathrm{I_2$(s)} to $$the equilibrium $$\mathrm{H_2$(g) + I_2$(s) \rightleftharpoons 2HI(g)}. $$What is the effect on the equilibrium?

Accepted Answer

No effect, because $$\mathrm{I_2$(s)} is in a $$different state.

Question 12

Which of the following is a correct application of collision theory to equilibrium shifts?

Accepted Answer

Increasing the concentration of a reactant increases the rate of the forward reaction.

Question 13

In the reversible reaction $$\mathrm{Hb(aq) + O_2$(aq) \rightleftharpoons $$HbO_2$$(aq)}$$, what happens in body tissues where $$\mathrm{O_2$}$$ concentration is low?

Accepted Answer

The equilibrium shifts to the left, releasing $$\mathrm{O_2$}.$$

Question 14

Which of the following will increase the yield of ammonia in the Haber process ($$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$)?

Accepted Answer

Decreasing the volume of the reaction vessel.

Question 15

For the endothermic decomposition $$\mathrm{(NH_4$)_2CO_3(s) \rightarrow 2NH_3(g) + CO_2$(g) + H_2O(g)}$$, what happens to the smell of ammonia as temperature increases?

Accepted Answer

It increases, because the equilibrium shifts to produce more $$\mathrm{NH_3$}.$$

Question 16

Which of the following changes will increase the value of the equilibrium constant $$K$$ for an exothermic reaction?

Accepted Answer

Decreasing the temperature.

Lesson 7.4: Le Châtelier’s Principle and Qualitative Changes in Chemical Equilibrium (12 Chem)

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