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Flashcards in Chapter 15 Test Deck (25)
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1
Q

Which of the following equilibrium expressions for the dissolution of calcium fluoride (CaF2 ) in water is correct?

A

Ksp = [Ca2+ ] [ F − ]^2

2
Q

When 1 mg of solid AgCl is dissolved in water, the following equilibrium is established with an equilibrium constant value of K1:
AgCl(s) <==> Ag+(aq) + Cl-(aq)
After equilibrium is established, an additional 9g of AgCl is added to the mixture. The equilibrium position shifts, and a new equilibrium is established with a equilibrium constant value of K2. How are K1 and K2 related?

A

K1 is equal to K2

3
Q

C(s) + CO2(g) <==> 2CO(g)
When this system is at equilibrium at 700 degrees C in a 1 L container, there are 0.2 mol CO, 0.4 mol CO2, and 0.8 mol C. When the system is cooled to 600 degrees C, an additional 0.04 mol C forms. Calculate the equilibrium constant at 700 degrees C and again at 600 degrees C.

A

Kc = 0.1 at 700 °C and Kc = 0.033 at 600 °C

4
Q

For the reaction
C(s) + CO2(g) <==> 2CO(g), Kp = 3.7. If the final total pressure is 2.78 atm, Which of the following shows the correct quadratic equation to solve for the change in partial pressure?

A

x ^2 + 3.7x − 10.3 = 0

5
Q

For the reaction N2O4(g) <==> 2NO2(g), Kp = 2.9 If the total pressure at equilibrium is 1.63 atm, what are the final partial pressure for the system at equilibrium?

A

1.16 atm (for NO2 ); 0.47 atm (for N2O4 )

6
Q

If the value of the equilibrium constant with regard to pressure (Kp ) is found to be 1.5 at 15°C, what is the value of the equilibrium constant with regard to concentration?
N2 + 2O2(g) <==> N2O4(g)
(R = 0.0821 L • atm / (mol • K))

A

8.4 × 10^2

7
Q

Which of the following factors will NOT disrupt a system at equilibrium?

A

leaving the reaction untouched for an infinite period of time

8
Q

For a reaction A+B -> AB, the value of the equilibrium constant is less than 1. Therefore, which of the following statements is correct?

A

Equilibrium lies toward the formation of the reactants.

9
Q

The ideal gas equation can be written as _______________

A

P = (n / V)RT

10
Q

In the ideal gas equation, the volume, V, ____________________

A

varies inversely with pressure

11
Q

Which statement best describes how the equilibrium constant and the reaction quotient can help a chemist?

A

They help a chemist evaluate in which direction a reaction will proceed in order to achieve equilibrium

12
Q

Look at the reaction of hydrogen and iodine to form HI gas.

H2(g) + I2(g) <==> 2HI(g)

Q is the reaction quotient. The value for Q at any point in this reaction is equal to [HI]2 / [H2 ] [ I2 ]. Which statement about Q is not correct?

A

The values for Q and Keq for the reaction are constant.

13
Q

Look at the following system.

PCl5(g) <==> PCl3(g) + Cl2(g)

Suppose that the equilibrium constant, KP, is 490 (at 340°C). If the partial pressure of PCl3 is 1.87 atm and the partial pressure of Cl2 is 0.29 atm, what is the partial pressure of PCl5?

A

0.0011 atm

14
Q

Look at the following equilibrium reaction of three gases.

N2(g) + 3H2(g) <==> 2NH3(g)

What would happen to the value of Q in this system if the volume was changed from 3 L to 9 L. If the system was at equilibrium at 3 L, in which direction would the reaction proceed to reach equilibrium at 9 L.

A

The new value for Q would be nine times the original value for Q. Therefore, the reverse reaction would occur in order to reach a new equilibrium.

15
Q

Which of the following statements about a catalyst is correct?

A

A catalyst affects the rate of reaction

16
Q

If the value of the equilibrium constant with regard to concentration (Kc ) is found to be 2.54 × 106 at 30°C, what is the value of the equilibrium constant with regard to pressure?
(R = 0.0821 L • atm / mol • K)
PCl3(g) + Cl2(g) <==> PCl5(g)

A

1.02 × 10^5

17
Q

What is the best definition of the reaction quotient, Q?

A

The reaction quotient is a measure of where a reaction “is at” at a given moment.

18
Q

Suppose that you have 38 L of components in a flask (at 400 degrees C). The components include 2.7 mol N2, 0.28 mol H2, and 1.3 mol NH3. If the equilibrium equation is N2(g) + 3H2(g) <==> 2NH3(g) (where Keq = 0.50 at 400 degrees C), which of the following shows the correct expression for the reaction quotient and the correct concentration values for each gas?

A
Q = [ NH3 ]2 / [ N2 ] [H2 ]^3;
[ NH3 ] = 0.034 mol / L;
[ N2 ] = 0.071 mol / L;
[H2 ] = 0.007 mol / L
19
Q

In the following reaction, CH4(g) + H2O(g) <==> CO(g) + 3H2(g) (where Kp = 1.8*10^-7 (at 600K)), assume that, initially , there is no methane. Assume also that you have large amounts of the two products. Which statement summarizes the predicted movement of the reaction as it shifts toward equilibrium?

A

The reaction will move to the left because there initially is no methane

20
Q

Why is it true that an equilibrium does not depend on where you start the reaction?

A

The substances will want to assume their most stable arrangement. This is achieved by the system moving to equilibrium.

21
Q

Look at the following ICE diagram problem. Which gas is the limiting reagent? CH4(g) + H2O(g) <==> CO(g) + 3H2(g)

A

CO

22
Q

H2(g) + I2(g) <==> 2HI(g) Kp = 92,.6 for this reaction. Suppose that you start with PH2 = 0.207 atm, PI2 = 0.191 atm, and PHI = 2.32 atm. You add H2 until its concentration reaches 0.299 atm. Let x equal the change in partial pressure of H2. What is the correct quadratic equation when solving for x in this reaction?

A

88.6x^2 - 54.7x - 0.10 = 0

23
Q

Suppose that you have a flask containing CH3 at a partial pressure of 2.3, H2O at a partial pressure of 1.5, CO at a partial pressure of 2.8, and H2 at a partial pressure of 0.3. What is the reaction quotient for this reaction? CH4(g) + H2O(g) <==> CO(g) + 3H2(g)

A

0.022

24
Q

Is the following statement true or false?

At high temperatures, enthalpy is a key component that determines where chemical equilibrium lies.

A

false

25
Q

The term dynamic equilibrium means___________

A

that reactants and products are continuously interconverting, though their concentration remains the same.

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