Question 1

Which of the following best describes the difference between the reaction quotient $$Q$$ and the equilibrium constant $$K$$ for a chemical reaction?

Accepted Answer

$$Q is $$calculated using the current concentrations or pressures, while $$K is $$constant for a given temperature and is calculated using equilibrium concentrations or pressures.

Question 2

Consider the reaction $$aW + bX \rightleftharpoons cY + dZ. $$The expression for the reaction quotient $$Q is$$:

Accepted Answer

$$Q = \frac{[Y]^c[Z]^d}{[W]^a[X]^b}$$

Question 3

A system is at equilibrium for the reaction $$\mathrm{Butane(g)} \rightleftharpoons \mathrm{Isobutane(g)}$$ with $$K_c = 2.50. If $$additional butane is suddenly added, what will happen to the concentration of isobutane as the system returns to equilibrium?

Accepted Answer

The concentration of isobutane will increase until equilibrium is reestablished.

Question 4

For the isomerization of trans-2-butene to cis-2-butene at 1000 K, $$K = 0.67. If $$you start with 5 molecules of each isomer, what will be the ratio of cis to trans isomers at equilibrium?

Accepted Answer

2:3

Question 5

If $$Q \u003e K$$ for a reaction, which of the following statements is true?

Accepted Answer

The reaction will proceed to the left, forming more reactants.

Question 6

Given the reaction $$\mathrm{$$PbCl_2$$(s) ightleftharpoons Pb$$^{2+}$$(aq) + 2Cl^-(aq)}$$ with $$K_1 = 1.7$$ 	imes $$10^{-5}$$, what is the equilibrium constant for the reverse reaction?

Accepted Answer

$$K = 5.88 	imes 10$$^{4}$$

Question 7

At 400 K, the equilibrium constant for the isomerization of cis-2-butene to trans-2-butene is $$K = 0.48. If $$you start with 1 bar of cis-2-butene and 0 bar of trans-2-butene, what will be the equilibrium partial pressure of trans-2-butene?

Accepted Answer

0.68 bar

Question 8

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

Accepted Answer

A system at equilibrium will adjust its composition to minimize the effect of a disturbance.

Question 9

For the reaction $$\mathrm{CH_4$(g) + H_2O(g) \rightleftharpoons CO(g) + 3H_2(g)}$$, what is the effect of removing water vapor using a drying agent?

Accepted Answer

The reaction will shift to the left to produce more reactants.

Question 10

If the volume of a reaction container is halved for a gaseous equilibrium, what is the general effect on the reaction quotient $$Q$$ for the reaction $$\mathrm{CH_4$(g) + H_2O(g) \rightleftharpoons CO(g) + 3H_2(g)}$$?

Accepted Answer

$$Q$$ increases by a factor of 4

Question 11

Which of the following scenarios would NOT change the value of the equilibrium constant $$K$$ for a reaction?

Accepted Answer

Adding a catalyst

Question 12

For the reaction $$2\mathrm{NaCl(s) \rightleftharpoons 2Na^+(aq) + 2Cl^-(aq)}$$, if $$K_2 = 36$ for $$\mathrm{NaCl(s) \rightleftharpoons Na^+(aq) + Cl^-(aq)}$$, what is the value of K_3$ for the doubled reaction?

Accepted Answer

$$K_3 = 1296$

Question 13

A reaction mixture initially contains only reactants. As the reaction proceeds, $$Q$$ increases and eventually equals $$K. $$What does this indicate?

Accepted Answer

The reaction has reached equilibrium.

Question 14

Which of the following best explains why $$K is $$constant for a given reaction at a fixed temperature?

Accepted Answer

$$K is a $$function of temperature and does not change unless the temperature changes.

Question 15

If a side reaction removes both a reactant and a product from a system at equilibrium, what can be predicted about the direction the main reaction will shift?

Accepted Answer

The direction cannot be predicted without more information.

Question 16

Which of the following is a correct statement about the effect of adding an inert gas (like argon) to a reaction at equilibrium in a constant-volume container?

Accepted Answer

It does not affect the equilibrium position.

Question 17

For the reaction $$\mathrm{cis-2-butene \rightleftharpoons trans-2-butene} at 1000 K $$with $$K = 0.67$$, which statement is true about the equilibrium mixture?

Accepted Answer

There will be more trans-2-butene than cis-2-butene.

Question 18

Which of the following best describes what happens to $$Q$$ and $$K$$ when a system at equilibrium is disturbed?

Accepted Answer

$$Q$$ changes, $$K$$ remains constant.

Chemical Equilibrium: Principles, Manipulation, and Le Châtelier’s Principle

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