Question 1

The graph shows the concentration of reactants and products over time for a reversible chemical reaction. What does the point where the two curves level off represent?

Accepted Answer

The system has reached dynamic equilibrium.

Question 2

Which equation correctly expresses the equilibrium constant $$K_c$$ for the reaction $$A(aq) + B(aq) \rightleftharpoons C(aq) + D(aq)$$?

Accepted Answer

$$K_c = \frac{[C][D]}{[A][B]}$$

Question 3

An avocado is left out and turns brown and mushy over time. Which chemical principle best explains why the browning process eventually slows and stops?

Accepted Answer

The reaction reaches dynamic equilibrium.

Question 4

For the reaction $$2H_2S(g) ightleftharpoons 2H_2(g) + S_2$(g)$$, if $$K_p = 2.4 	imes 10$$^{-4}$$ at 1073 K and $$\Delta n = 1$$, what is the value of K_c$? (Use R = 0.08206$ L·atm·mol$$^{-1}$$·K$$^{-1}$$)

Accepted Answer

$$K_c = 2.7 	imes 10$$^{-6}$$

Question 5

Which of the following changes will NOT affect the equilibrium position of a reaction according to LeChatelier’s Principle?

Accepted Answer

Adding a catalyst

Question 6

For the reaction $$H_2(g$$) + $$I_2(g$$) \rightleftharpoons 2HI(g)$$, if $$[$$H_2$$] = 1.0$$ M, $$[$$I_2$$] = 1.0$$ M, $$[HI] = 1.0$$ M, and K_c = 50$, what is the value of Q_c$ and which way will the reaction shift?

Accepted Answer

$$Q_c = 1.0$$, shift to products

Question 7

Which statement about equilibrium constants is correct?

Accepted Answer

If $$K \gg 1$$, the reaction mixture at equilibrium will contain mostly products.

Question 8

For a gas-phase reaction, under what condition will $$K_p = K_c$$?

Accepted Answer

When $$\Delta n = 0$$

Question 9

A catalyst is added to a reaction mixture at equilibrium. What effect does this have?

Accepted Answer

It causes the system to reach equilibrium faster

Question 10

For the reaction $$A(aq) + B(aq) \rightleftharpoons C(aq) + D(aq)$$, if at equilibrium $$[A] = 1.0 M$$, $$[B] = 2.0 M$$, $$[C] = 6.0 M$$, $$[D] = 3.0 M$$, what is $$K_c$$?

Accepted Answer

$$K_c = 9.0$$

Question 11

If the volume of a container is increased for the reaction $$A(g) + B(g) \rightleftharpoons C(g)$$, what will happen to the equilibrium?

Accepted Answer

The reaction will shift toward more moles of gas (products)

Question 12

Which of the following is NOT included in the equilibrium constant expression?

Accepted Answer

Pure solids

Question 13

For the reaction $$C_p$$^{2+}$$ + S_r$$^{3+}$$ \rightleftharpoons C_p$$^{3+}$$ + S_r$$^{2+}$$, if all ion concentrations are 1.0 M and K_c = 2.0$, what will happen?

Accepted Answer

The reaction will shift to the right, making more products.

Question 14

If an inert gas is added to a reaction mixture at constant volume, what effect does it have on the equilibrium?

Accepted Answer

No effect

Question 15

For an exothermic reaction, what happens if the temperature is increased?

Accepted Answer

The equilibrium shifts toward reactants.

Question 16

Which scenario best illustrates LeChatelier’s Principle?

Accepted Answer

Removing a product causes the reaction to produce more product.

Question 17

For the reaction $$A(g) + B(g) \rightleftharpoons C(g)$$, what happens to $$Q if $$the volume is doubled?

Accepted Answer

$$Q$$ increases and the reaction shifts to make more reactants.

Question 18

Which of the following is a correct method for combining equilibrium constants for coupled reactions?

Accepted Answer

Multiply the $$K$$ values of all source reactions.

Question 19

If a reaction is reversed, how is the equilibrium constant $$K$$ affected?

Accepted Answer

It becomes the reciprocal $$K^{-1}.$$

Question 20

For the reaction $$A(aq) + B(aq) \rightleftharpoons C(aq) + D(aq)$$, if $$K_c = 9.0$$ and $$[A] = [B] = [C] = 2.0 M$$, what is the equilibrium concentration of $$D$$?

Accepted Answer

$$[D] = 18 M$$

L24 Chemical Equilibrium and Le Chatelier’s Principle: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards