Question 1

Which of the following best explains why storing milk in the fridge keeps it fresh longer, as shown in the image?

Accepted Answer

Lower temperature decreases the rate of chemical reactions responsible for spoilage.

Question 2

A natural gas detector is used to prevent explosions in homes. Which factor of chemical kinetics does this relate to?

Accepted Answer

Concentration of reactants: higher gas concentration increases reaction rate, leading to explosion risk.

Question 3

For the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightarrow 2 HI(g)}$$, the rate can be defined using either reactant or product. Which equation correctly expresses the rate in terms of $$\mathrm{[HI]}$$?

Accepted Answer

$$\mathrm{rate = \frac{1}{2} \frac{\Delta [HI]}{\Delta t}}$$

Question 4

A reaction $$\mathrm{A \rightarrow B} is $$known to be second-order. If the rate is $$0.15\ \mathrm{M/s} at$$ $$[A] = 0.100\ \mathrm{M}$$, what is the rate at $$[A] = 0.230\ \mathrm{M}$$?

Accepted Answer

$$0.79\ \mathrm{M/s}$$

Question 5

Which statement about the effect of concentration on reaction rate is correct?

Accepted Answer

Higher concentration leads to more frequent collisions and a higher reaction rate.

Question 6

What is the unit of the rate constant $$k$$ for a first-order reaction?

Accepted Answer

$$\mathrm{1/s}$$

Question 7

Which of the following best describes the activation energy in a chemical reaction?

Accepted Answer

The minimum energy required for reactant molecules to successfully collide and form products.

Question 8

In the context of chemical kinetics, what does the term 'instantaneous rate' refer to?

Accepted Answer

The rate of reaction at a specific moment, calculated as $$\mathrm{\frac{d[A]}{dt}}.$$

Question 9

For the reaction $$\mathrm{A + 2B \rightarrow C}$$, if the rate is $$0.100\ \mathrm{M/s}$$, what is $$\mathrm{\frac{\Delta [B]}{\Delta t}}$$?

Accepted Answer

$$-0.200\ \mathrm{M/s}$$

Question 10

Which factor does NOT generally increase the rate of a chemical reaction?

Accepted Answer

Decreasing the temperature.

Question 11

A reaction is found to be zero order in reactant A. What happens to the rate if $$[A] is $$doubled?

Accepted Answer

The rate remains unchanged.

Question 12

Which scenario best illustrates the importance of molecular orientation in chemical reactions?

Accepted Answer

Only collisions with proper orientation lead to product formation, even if energy is sufficient.

Question 13

For a reaction with the rate law $$\mathrm{rate = k[A]^{1.5}[B]^0}$$, what is the overall order of the reaction?

Accepted Answer

1.5

Question 14

Which of the following is a correct method to experimentally determine the order of a reaction with respect to a reactant?

Accepted Answer

Vary the concentration of one reactant while keeping others constant and observe the change in rate.

Question 15

If a reaction is first-order in A, what happens to the rate if $$[A] is $$tripled?

Accepted Answer

The rate triples.

Question 16

Which graph best represents the change in reactant concentration over time for a second-order reaction?

Accepted Answer

A curve that decreases more slowly at first and then more rapidly, as shown in $$\mathrm{[A]} vs. $$time for $$n=2.$$

Question 17

Which of the following statements about the rate law is correct?

Accepted Answer

The rate law must be determined experimentally and cannot be inferred from stoichiometry.

Question 18

In a reaction where the rate law is $$\mathrm{rate = k[$$CHCl_3$$]^1[Cl_2$]^{0.5}}$$, what is the order with respect to $$\mathrm{Cl_2$}$$?

Accepted Answer

0.5

Question 19

Why are powdered solids often more reactive than solid blocks?

Accepted Answer

Powdered solids have greater surface area, increasing the frequency of collisions.

Chemical Kinetics: Reaction Rates and Rate Laws

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