Equilibrium Unit 7 Review

Two sealed containers hold equal volumes of methanol at the same temperature. Container A has a larger surface area than Container B. The vapor pressure of methanol is:

• Higher in container A due to the greater surface area

• Higher in container B because the liquid level is higher

• • Higher in container B because the volume of vapor is smaller

• The same in both, as temperature and liquid volume are identical

• The same in both, as it depends only on the liquid's identity

Answer explanation

Vapor pressure is determined by the temperature and the identity of the liquid, but not directly affected by the surface area or the volume of the container. As both containers hold equal volumes of methanol at the same temperature, the vapor pressure of methanol will be the same in both containers. The surface area and the volume of the container do not affect the vapor pressure of the liquid inside.

The reaction below occurs at a certain temperature: CO2(g) + H2(g) ⇄ CH4(g) + H2O(g) ΔH < 0

The Kc for the reaction is 18.5. Initially, a mixture of CO2(g) and H2(g) has a combined pressure of 1.8 atm. What's the total equilibrium pressure if the volume is doubled (temperature stays constant)?

• Less than 1.8 atm

• Between 1.8 and 3.6 atm

• 3.6 atm

• Greater than 3.6 atm

A reaction between P2(g) and Q(g) is placed in a container at constant temperature: P2(g) + 2Q(g) ⇄ 2PQ(g)

Data is collected:

Time (minutes) [P2] (M) [Q] (M) [PQ] (M)

0 0.50 0.30 0.00

30 0.35 0.10 0.30

60 0.30 0.05 0.40

90 0.30 0.05 0.40

Which statement is most likely correct?

• Equilibrium was reached by 15 minutes, as [P2] and [Q] were similar.

• • Equilibrium was reached between 60 and 90 minutes, where concentrations remained constant.

• Equilibrium was not reached because only 70% of the initial P2 was consumed.

• Equilibrium was not reached because [PQ] needs to be higher.

The following reaction occurs at 350 K: X(g) + 2Y(g) ⇄ 2Z(g)

The molar concentrations at equilibrium are: [X] = 1.0 M, [Y] = 0.8 M, and [Z] = 3.0 M. What is the equilibrium constant for the reaction at 350 K?

• 0.44

• 1.8

• 2.3

• 14

• 17

Consider the equilibrium of two isomers of substance W: W1(g) ⇄ W2(g)

At a certain temperature, the initial concentration of W1 is 3.0 M and the equilibrium concentration is 2.2M. In a second experiment at the same temperature, the initial W1 concentration is 1.0M. Which statement about the equilibrium concentration of W1 in the second experiment is likely correct?

• It's about 0.2M, as the Kc should be the same.

• It's about 0.8M, because the ratio [W2]/[W1] should remain constant.

• • It's less than 0.8M because, with less reactant present initially, less product will form.

• • It can't be determined, as the temperature may have changed.

A 2.0-mole sample of X2 and a 1.0-mole sample of Y2 are placed in a previously evacuated 2.0L container and allowed to reach the equilibrium:

X2(g) + Y2(g) ⇄ 2XY(g)

If 0.6 moles of XY are present at equilibrium, what's the approximate value of the equilibrium constant?

• 0.3

• 0.6

• 1.2

• 2.4

Consider the stepwise formation of the complex ion [Co(H2O)6]2+:

Co2+(aq) + H2O(l) ⇄ [Co(H2O)6]2+(aq)

Subsequent steps involve replacing one H2O with another ligand (let's use Cl-):

[Co(H2O)6]2+(aq) + Cl-(aq) ⇄ [Co(H2O)5Cl]+(aq) + H2O(l) ...and so on

Which Ag species will have the highest concentration in the equilibrium system shown below, and why?

[Co(H2O)6]2+(aq) + 4Cl-(aq) ⇄ [CoCl4]2- (aq) + 6H2O(l)

• [Co(H2O)6]2+ , because each stepwise equilibrium constant is large

• • [Co(H2O)6]2+ , because adding Cl- drives the equilibrium left

• [CoCl4]2-, because its formation is highly favored overall

• [CoCl4]2-, because the overall equilibrium lies far to the right

Three reactions at the same temperature are given:

Reaction 1: A(g) + 2B(g) ⇄ 2C(g) Kc1 = 5.0
Reaction 2: C(g) ⇄ 1/2 D(g) Kc2 = 2.0 Reaction 3: D(g) + B(g) ⇄ E(g) Kc3 = 0.5

Which expression can be used to find Kc for: A(g) + 3B(g) ⇄ 2E(g)

• Kc1 * Kc2 * Kc3

• Kc1 * (Kc2)² * (1/Kc3)

• Kc1 * (1/Kc2)² * Kc3

• Cannot be determined from the given information

The equilibrium constant for the reaction below is 20.0 at a certain temperature:

2F(g) ⇄ F2(g)

What's the equilibrium constant for this reaction at the same temperature?

F2(g) ⇄ 2F(g)

• 0.050

• 5.0

• 10

• 400

A vessel initially contains:

• X(g) at 0.30 atm

• Y(g) at 0.50 atm

• Z(g) at 0.10 atm

The reaction below occurs, with Kp = 2.5 at the given temperature:

X(g) + 2Y(g) ⇄ 3Z(g)

How will partial pressures change as equilibrium is approached?

• X and Y increase, Z decreases, because Q > Kp

• X and Y decrease, Z increases, because Q < Kp

• • X and Y decrease, Z increases, because the reaction shifts right

• X and Y increase, Z decreases, because pressure favors the side with fewer moles