Q: For the reaction $$2\text{CO}(g) + 4\text{H}_2\text{O}(g) \rightleftharpoons 2\text{CH}_4(g) + 3\text{O}_2(g)$$, which is the correct expression for the equilibrium constant $$K_c$$?

$$K_c = \frac{[\text{CH}_4]^2[\text{O}_2]^3}{[\text{CO}]^2[\text{H}_2\text{O}]^4}$$

Question 1

Refer to the periodic table section shown in the first image. Which of the following statements best describes the elements highlighted in the staircase region?

Accepted Answer

They are metalloids, exhibiting properties of both metals and nonmetals.

Question 2

The graph in the second image shows concentration versus time for three reactions. Which curve (black, blue, or red) represents a zeroth-order reaction?

Accepted Answer

The black curve.

Question 3

The reaction progress diagram in the third image shows a single peak. What does the height of the peak represent?

Accepted Answer

The activation energy, $$E_a$$, for the reaction.

Question 4

Consider the four sets of boxes in the fourth, fifth, sixth, and seventh images, each showing a reaction A $$\rightleftharpoons B $$over time. Which experiment(s) have reached equilibrium?

Accepted Answer

All except the third experiment (sixth image).

Question 5

In the context of the molecular diagrams (eighth to eleventh images), which reaction is most product-favored at equilibrium?

Accepted Answer

A$$_2 + B$_2$$ $$\rightleftharpoons 2 AB ($$eighth image)

Question 6

Given the concentration vs. time plot for A $$\rightleftharpoons B in $$the twelfth image, what can you conclude about the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c is $$between 0 and 1.

Question 7

A reaction is monitored and the plot of $$\ln [A]$$ versus time is linear. Which of the following is true about the reaction?

Accepted Answer

The reaction is first order.

Question 8

For a reaction with the rate law $$	ext{Rate} = k[A][B]^2$$, what would happen to the rate if the concentration of B is doubled while A remains constant?

Accepted Answer

The rate would quadruple.

Question 9

Which part of the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$ accounts for the fraction of collisions with the correct orientation?

Accepted Answer

The frequency factor, $$A$$

Question 10

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternate pathway with a lower activation energy.

Question 11

For the reaction $$2	ext{CO}(g) + 4	ext{H}_2	ext{O}(g) ightleftharpoons 2	ext{CH}_4(g) + 3	ext{O}_2(g)$$, which is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \frac{[	ext{CH}_4]^2[	ext{O}_2]^3}{[	ext{CO}]^2[	ext{H}_2	ext{O}]^4}$$

Question 12

If $$K_c = 0.11 at$$ $$25^\circC $$for the reaction $$	ext{N}_2	ext{O}_4(g) ightleftharpoons 2	ext{NO}_2(g)$$, what is $$K_c$$ for the reaction $$6	ext{NO}_2(g) ightleftharpoons 3	ext{N}_2	ext{O}_4(g)$$?

Accepted Answer

0.0013

Question 13

A student observes that doubling the concentration of reactant A in a reaction doubles the rate, while doubling B quadruples the rate. What is the rate law for this reaction?

Accepted Answer

Rate = $$k[A][B]^2$$

Question 14

For a first-order reaction, which of the following is true about the half-life?

Accepted Answer

It remains constant throughout the reaction.

Question 15

A reaction mechanism has a slow initial step followed by a fast step. Which step determines the overall rate law?

Accepted Answer

The slow step.

Question 16

Which of the following best describes the effect of increasing temperature on the rate constant $$k$$ according to the Arrhenius equation?

Accepted Answer

The rate constant increases.

Question 17

In a reaction progress diagram with multiple peaks, what do the valleys between the peaks represent?

Accepted Answer

Intermediates.

Question 18

Which of the following is a correct statement about chemical equilibrium?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 19

A reaction is found to be zeroth order in A. If the initial concentration of A is doubled, what happens to the half-life?

Accepted Answer

It doubles.

Practice Exam Guidance: Chemical Kinetics & Equilibrium (C117)

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