AP Chemistry: 7.2 Direction of Reversible Reactions – Exam Style questions with Answer- MCQ

Question

                        

                                              \(AgCl(s)⇄Ag^+(aq)+Cl^−(aq)\)

When \(AgCl(s)\) is placed in water, it dissolves according to the chemical equation above. The particle diagram above was proposed to represent an aqueous solution in which \(AgCl(s)\)is in equilibrium with its ions. Which of the following best explains whether or not the diagram provides a good representation of this dynamic equilibrium at the microscopic level?

A It is a good representation because it shows that the dipoles of the \(H_2O\) molecules are oriented around the \(Ag^+\) and \(Cl^−\) ions in solution.

B It is a good representation because it shows that the concentrations of \(Ag^+\) ions and \(Cl^−\) ions are equal at equilibrium.

C It is not a good representation because it does not show that the concentration of \(AgCl(s)\) is constant at equilibrium.

D It is not a good representation because it does not illustrate the dynamic equilibrium in which the rates of the forward and reverse reactions are equal.

▶️Answer/Explanation

Ans:D

Since at equilibrium the rates of the forward and reverse reactions are the same, one single representation cannot capture the dynamic nature of this process. Multiple representations of the reaction before and after equilibrium would be needed to show that the concentrations of the ions have remained constant over time.

Question

                                                                

The particle diagram above shows the system represented by the equation \(2X(g)+Y_2(g)\)⇄\(2XY(g)\) . Which of the following explains whether the particle diagram indicates that the system is at equilibrium?

A The particle diagram does not indicate that the system is at equilibrium because it shows the system only at one point in time.

B The particle diagram does not indicate that the system is at equilibrium because the ratio \(\frac{[XY]_{eq}}{[X]_{eq}}\) is not equal to 1.

C The particle diagram indicates that the system is at equilibrium because the value of K is small.

D The particle diagram indicates that the system is at equilibrium because \([XY]_{eq}=2×[Y_2]_{eq}\).

▶️Answer/Explanation

Ans:A

Equilibrium is a dynamic process in which the rates of the forward reaction and the reverse reaction are equal and the concentrations of reactants and products remain constant over time. A single representation cannot capture this dynamic process.

Question

                                 

                                                                                   \(X(g)+Y(g)\)⇄\(XY(g)\)

The particle diagrams above show the changes that occurred after an equimolecular mixture of X(g) and Y(g) was placed inside a rigid container at constant temperature. Which of the following statements is be best supported by the particle diagrams?

A The rate of the reverse reaction is zero because the concentration of XY keeps increasing.

B The reverse reaction has a higher rate than the forward reaction between 200s and 300s because [XY]>>[X].

C The forward reaction has a faster rate than the reverse reaction between 0s and 300s because more products were being formed.

D The rates of the forward and reverse reactions were the same after 100s because the rate of formation of XY was constant.

▶️Answer/Explanation

Ans:C

Based on the particle diagrams, the amount of XY kept increasing between 0s and 300s, indicating that the forward reaction occurred at a faster rate than the reverse reaction.

Question

\(X_{2}+Y_{2}(g)\rightleftharpoons 2XY(g) k_{c}=3.0\)

A mixture of\( X_{2}\)(g), \(Y_2\)(g), and XY(g) is placed in a previously evacuated, rigid container and allowed to reach equilibrium at a constant temperature, as shown above. Which of the following sets of initial concentrations would lead to the formation of more product as the system moves toward equilibrium?

▶️Answer/Explanation

Ans:A

Question

Which of the following happens to H atoms in the forward reaction?

(A) H atoms are oxidized only.

(B) H atoms are reduced only.

(C) H atoms are both oxidized and reduced.

(D) H atoms are neither oxidized nor reduced.

▶️Answer/Explanation

Ans:C

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