Q: A reaction is found to be zero order with respect to $$[\text{I}_2]. $$What does this imply about the effect of $$[\text{I}_2] on $$the rate?

The rate is independent of $$[\text{I}_2].$$

Question 1

For the reaction $$aA + bB ightarrow cC + dD$$, the experimentally determined rate law is $$	ext{Rate} = k[A]^2[B]. If $$the concentration of A is doubled and B is kept constant, by what factor does the rate increase?

Accepted Answer

The rate increases by a factor of 4.

Question 2

Which of the following statements about reaction order is TRUE?

Accepted Answer

The overall order of a reaction is the sum of the exponents in the rate law.

Question 3

Given the rate law $$	ext{Rate} = k[	ext{CH}_3	ext{COCH}_3]^x[	ext{H}^+]^y[	ext{I}_2]^z$$, if experimental data shows that doubling $$[	ext{I}_2]$$ does not change the rate, what is the value of $$z$$?

Accepted Answer

$$z = 0$$

Question 4

The Arrhenius equation is $$\ln k = -\frac{E_a}{R}\frac{1}{T} + \ln a. $$What does the slope of a plot of $$\ln k$$ versus $$1/T$$ represent?

Accepted Answer

The negative activation energy divided by the gas constant, $$-E_a/R$$

Question 5

In the iodination of acetone experiment, why is it important to bring both the beaker and flask to the same temperature before mixing?

Accepted Answer

To ensure that the measured rate reflects the intended temperature, avoiding errors due to temperature differences.

Question 6

If the rate law for a reaction is $$	ext{Rate} = k[A]^{1/2}[B]^2$$, what are the units of $$k$$?

Accepted Answer

$$\mathrm{M}^{-2.5}\mathrm{s}^{-1}$$

Question 7

A student runs the iodination of acetone at two temperatures and obtains rate constants $$k_1$$ and $$k_2 at$$ $$T_1$$ and $$T_2$$, respectively. Which equation would allow them to calculate the activation energy, $$E_a$$?

Accepted Answer

$$\ln\left(\frac{k_2$}{k_1$}\right) = -\frac{E_a}{R}\left(\frac{1}{T_2$} - \frac{1}{T_1$}\right)$$

Question 8

During the experiment, why is starch used as an indicator in the iodination of acetone?

Accepted Answer

Starch forms a blue complex with iodine, allowing visual detection of iodine disappearance.

Question 9

Which of the following is affected by a change in temperature? (Select the best answer.)

Accepted Answer

Both reaction rate, $$R$$, and rate constant, $$k$$

Question 10

A reaction is found to be zero order with respect to $$[	ext{I}_2]. $$What does this imply about the effect of $$[	ext{I}_2] on $$the rate?

Accepted Answer

The rate is independent of $$[	ext{I}_2].$$

Question 11

In the experiment, why is it important to avoid preparing more than two trials per mixture at a time?

Accepted Answer

To avoid loss of volatile components and ensure accuracy of results.

Question 12

If the experimentally determined rate law for the iodination of acetone is $$	ext{Rate} = k[	ext{CH}_3	ext{COCH}_3]^1[	ext{H}^+]^1[	ext{I}_2]^0$$, what is the overall order of the reaction?

Accepted Answer

Second order

Question 13

A student calculates the rate of reaction using $$	ext{Rate} = -\frac{\Delta [	ext{I}_2]}{\Delta t}. $$What assumption is made in this calculation?

Accepted Answer

The rate is constant throughout the reaction.

Question 14

Which of the following best describes the purpose of constructing an Arrhenius plot ($$\ln k vs$$. $$1/T) in $$this experiment?

Accepted Answer

To determine the activation energy, $$E_a$$, for the reaction.

Question 15

Which of the following is a correct safety procedure when handling iodine solutions in this experiment?

Accepted Answer

Neutralize spills with 5% $$	ext{Na}_2	ext{S}_2	ext{O}_3$$ solution.

Question 16

If the rate law for a reaction is $$	ext{Rate} = k[A]^1[B]^0$$, and the initial rate is $$0.020\ \mathrm{M/s}$$ when $$[A] = 0.10\ \mathrm{M}$$, what is the rate when $$[A] = 0.30\ \mathrm{M}$$ and $$[B] is $$unchanged?

Accepted Answer

$$0.060\ \mathrm{M/s}$$

Question 17

Which of the following metals is commonly used in automobile catalytic converters?

Accepted Answer

Platinum

Question 18

Which species acts as a catalyst in the destruction of ozone in the atmosphere?

Accepted Answer

Chlorine atom ($$	ext{Cl})$$

Question 19

A student finds that the rate constant $$k$$ for a reaction doubles when the temperature increases from $$300\ \mathrm{K} to$$ $$310\ \mathrm{K}. $$What does this suggest about the activation energy, $$E_a$$?

Accepted Answer

$$E_a is $$positive and significant.

Question 20

Why is it important to cover reagent bottles and burets containing volatile solutions when not in use during the experiment?

Accepted Answer

To minimize evaporation and maintain accurate concentrations.

Reaction Kinetics: The Iodination of Acetone – Rate Laws and Activation Energy

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