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AP® Chemistry

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Components of a Mechanism

APCHEM-UJ1ZVD

$$\text{Step 1:} \ Cl_2⇔ 2Cl$$

$$\text{Step 2:} \ CH_4+ Cl → CH_3+ HCl \ \text{(slow)}$$

$$\text{Step 3:} \ CH_3+ Cl_2→ CH_3Cl + Cl$$

$$\text{Step 4:} \ CH_3Cl + Cl → CH_2Cl_2+ H$$

$$\text{Step 5:} \ H + Cl → HCl$$

The above mechanism shows the overall reaction between chlorine gas and methane gas to form dichloromethane gas and hydrogen monochloride gas. The reaction is carried out in the gas state with no ions being formed during the reaction.

Which of the following statements is NOT supported by the mechanism?

A

$CH_3Cl$ is an intermediate because it is made in Step 3 and used in Step 4.

B

The order of the reaction with respect to $CH_4$ is one since Step 2 is the slowest step, making the rate law for Step 2 the following: $\text{rate} =k [CH_4][Cl]$.

C

The first step is the only equilibrium step in the reaction.

D

The overall rate law for the reaction is: $\text{rate} =k[CH_4][Cl_2]$.