AP MCQ 07ABCDEFGHIJKLMN PART 1

Question 01:

It is observed that when hexaaquacobalt(II) ions are exposed to chloride ions, that the reaction shown below occurs, and when equilibrium has been established, that the beaker’s contents are purple in color. What does the observation of a purple color alone, suggest about the equilibrium reaction mixture?

[Co(H₂O)₆]²⁺_(aq) (red) + 4Cl^-_(aq) ⇌ [CoCl₄]^2-_(aq) (blue) + 6H₂O_(l)

The equilibrium mixture is made up of 50% red species and 50% blue species
The equilibrium contains both red and blue species but in unknown amounts
The equilibrium mixture lies heavily to the left
The equilibrium mixture lies heavily to the right

Question 02:

Which expression correctly characterizes the relationship between Q and K at equilibrium?

Q = K
Q = -K
Q^-1 = K
Q = K^-1

Question 03:

What is true of any reversible reaction reaction that has reached equilibrium?

All products and reactants will have the same concentrations
The reaction has stopped
There is a specific ratio of products to reactants at a specific temperature
Less products will be produced if the reaction is cooled

Questions 04-06:

The chemical reaction below has Kc = 5.0 at a temperature of 2000 K.

H_2(g) + CO_2(g) ⇌ H₂O_(g) + CO_(g)

In an experiment, 2.0 moles of H_2(g), 2.0 moles of CO_2(g), 1.0 mole of H₂O_(g) and 1.0 mole of CO_(g) are brought together in a 1.0 L container at 2000 K.

Question 04:

What happens to the concentration of CO_2(g), as the mixture approaches equilibrium?

It remains at 2.0 M, since the reaction mixture is already at equilibrium because Kc is fixed at a fixed temperature
It remains at 2.0 M, since the reaction is already at equilibrium
It decreases since the reaction will proceed forward in order to reach equilibrium
It increases since the reaction will proceed backward in order to reach equilibrium

Question 05:

Once equilibrium has been established at 2000 K, what would be the effect on Kc, and the effect on the concentration of CO_(g), if a sample of hydrogen gas were injected into the reaction vessel in such a way that the temperature remained constant and the system was allowed to reach equilibrium once more?

[CO_(g)] increases and K decreases
[CO_(g)] increases and K remains constant
[CO_(g)] increases and K increases
[CO_(g)] decreases and K remains constant

Question 06:

What is the Kc for the reaction shown below?

2H₂O_(g) + 2CO_(g) ⇌ 2H_2(g) + 2CO_2(g)

10
25
1/10
1/25

Question 07:

A weak diprotic acid, H₂X, is known to dissociate in two separate steps. If the equilibrium constant for step 1 (the loss of one H⁺ ion) is called A, and the equilibrium constant for step 2 (the loss of the second proton from HX^-) is called B, What is the equilibrium constant for the reaction below?

H₂X ⇌ 2H⁺ + X^-

(A)+(B)
(A)/(B)
(A)(B)
(B)/(A)

Question 08:

Which of the following changes cause the equilibrium constant K, for any reaction, to change?

Adding products to the equilibrium mixture
Adding reactants to the equilibrium mixture
Changing the temperature
Increasing the pressure while keeping all other variables the same

Question 09:

1 mole of PCl_5(g) introduced into and evacuated container and is heated until the following equilibrium is established. Which of the following statements is true?

PCl_5(g) ⇌ PCl_3(g) + Cl_2(g)

At equilibrium the total moles in the container will be greater than 1
PCl₃ and Cl₂ will be present in differing amounts
The amount of PCl_5(g) will remain constant
As the reaction proceeds from the initial conditions to the equilibrium position, the mole fraction of PCl_3(g) decreases

Question 10:

At a particular temperature, the equilibrium partial pressures of SO_2(g), O_2(g) and SO_3(g) in the equilibrium mixture shown below, are found to be 1.0 atm, 0.5 atm and 3.0 atm respectively. What is the value of Kp at this temperature?

2SO_2(g) + O_2(g) ⇌ 2SO_3(g)