Question 1

Which statement best describes chemical equilibrium in the context of the reaction: $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}$$?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

According to Le Chatelier’s Principle, what will happen if more $$\mathrm{HF} is $$added to the equilibrium mixture: $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}$$?

Accepted Answer

The reaction will shift to the right, producing more $$\mathrm{F^-}$$ and $$\mathrm{H_3O^+}.$$

Question 3

If $$\mathrm{F^-} is $$removed from the equilibrium mixture $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}$$, what is the predicted shift according to Le Chatelier’s Principle?

Accepted Answer

The reaction will shift to the right, producing more $$\mathrm{F^-}$$ and $$\mathrm{H_3O^+}.$$

Question 4

A patient’s blood pH drops due to increased $$\mathrm{CO_2$}. $$Using Le Chatelier’s Principle, predict the shift in the equilibrium: $$\mathrm{CO_2$(aq) + H_2O(l) \rightleftharpoons H_2CO_3(aq) \rightleftharpoons $$HCO_3$$^-(aq) + H^+(aq)}.$$

Accepted Answer

The equilibrium shifts right, increasing $$\mathrm{H^+}.$$

Question 5

Which of the following best explains why the concentrations of reactants and products remain constant at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 6

For the reaction $$\mathrm{$$HCHO_2$$(aq) + H_2O(l) \rightleftharpoons $$CHO_2$$^-(aq) + H_3O^+(aq)}$$, what happens if $$\mathrm{$$CHO_2$$^-} is $$added?

Accepted Answer

The reaction shifts to the left, producing more $$\mathrm{$$HCHO_2$$}.$$

Question 7

A student removes $$\mathrm{H_3O^+}$$ from the equilibrium mixture $$\mathrm{$$HCHO_2$$(aq) + H_2O(l) \rightleftharpoons $$CHO_2$$^-(aq) + H_3O^+(aq)}. $$What is the effect?

Accepted Answer

The reaction shifts to the right, producing more $$\mathrm{H_3O^+}.$$

Question 8

Which of the following is a real-life example of Le Chatelier’s Principle in the human body?

Accepted Answer

The body increases breathing rate to remove excess $$\mathrm{CO_2$}$$, shifting the equilibrium $$\mathrm{CO_2$ + H_2O \rightleftharpoons H_2CO_3} to $$the left.

Question 9

If the concentration of $$\mathrm{$$HCHO_2$$} is $$decreased in the equilibrium $$\mathrm{$$HCHO_2$$(aq) + H_2O(l) \rightleftharpoons $$CHO_2$$^-(aq) + H_3O^+(aq)}$$, what will happen?

Accepted Answer

The reaction shifts to the left.

Question 10

Which of the following best describes a reversible reaction?

Accepted Answer

A reaction where products can reform reactants.

Question 11

A chemist adds $$\mathrm{F^-} to $$the equilibrium mixture $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}. $$What is the effect?

Accepted Answer

The reaction shifts to the left, producing more $$\mathrm{HF}.$$

Question 12

Which of the following is NOT a way to disturb equilibrium according to Le Chatelier’s Principle?

Accepted Answer

Allowing the reaction to reach equilibrium and then doing nothing.

Question 13

In a hospital, a patient is given a buffer solution to maintain blood pH. Which principle explains how the buffer resists changes in pH when small amounts of acid or base are added?

Accepted Answer

Le Chatelier’s Principle

Question 14

Which of the following best describes the effect of removing $$\mathrm{HF}$$ from the equilibrium mixture $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}$$?

Accepted Answer

The reaction shifts to the left, producing more $$\mathrm{HF}.$$

Question 15

Which of the following is true at equilibrium for the reaction $$\mathrm{HF(aq) + H_2O(l) \rightleftharpoons F^-(aq) + H_3O^+(aq)}$$?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Acid-Base Equilibrium and Le Chatelier’s Principle

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