# Quiz 2 - Chemical Kinetics: Rate Laws | Chemical Kinetics: Rate Laws

## General Chemistry 2 - Quiz 2 - Chemical Kinetics: Rate Laws

What is the rate of the following reaction: 2A + B → C?

A is a reagent and its stochiometric coefficient is 2. Reaction rate of a reagent:

- $\frac{1}{\mathrm{\alpha}}\frac{\u2206\left[\mathrm{reagent}\right]}{\u2206\mathrm{t}}$

α = stochiometric coefficient

[reagent] = concentration of the reagent (in mol.L^{-1})

What is the overall order of a reaction with a rate = k [A]^{2 }[B]?

The overall order of reaction is the sum of the orders of reaction of all the reactants

What are the units of the constant k in the rate of reaction = k [A]^{2 }[B] (concentration in mol.L^{-1}) ?

The rate of reaction is in mol.L^{-1}.s^{-1} and [A]^{2 }[B] is in mol^{3}.L^{-3} ⇒ k is in mol^{-2}.L^{2}.s^{-1}

What is correct concerning the half-time of a first-order reaction?

For a first-order reaction: ${\mathrm{t}}_{1/2}=\frac{\mathrm{ln}2}{\mathrm{k}}$

What is correct concerning the half-time of a second-order reaction?

For a second-order reaction: ${\mathrm{t}}_{1/2}=\frac{1}{\mathrm{k}{\left[\mathrm{A}\right]}_{0}}$

What is the relationship between [A] and t for a first-order reaction?

For a first-order reaction: $-\frac{\u2206\left[\mathrm{A}\right]}{\u2206\mathrm{t}}$ = k [A]

After integrating: ln [A] = ln [A]_{0} - kt ⇒ $\frac{\left[\mathrm{A}\right]}{{\left[\mathrm{A}\right]}_{0}}$ = e^{-kt}

Which of the following best describes the reaction rate?

The reaction rate is defined as the change in concentration of a reactant or product per unit time.

In the context of radioactive decay, which order of kinetics does radioactive decay generally follow?

Radioactive decay generally follows first-order kinetics, where the rate of decay is proportional to the amount of substance present.

Which of the following is the correct integrated rate law expression for a second-order reaction?

For a second-order reaction, the integrated rate law is $\frac{1}{\left[\mathrm{A}\right]}$ = $\frac{1}{{\left[\mathrm{A}\right]}_{0}}$ + kt, where k is the rate constant, [A]_{0} is the initial concentration, and [A] is the concentration at time t.

If the half-life of a radioactive isotope is 5 years, what fraction of the original sample will remain after 20 years?

After 20 years (which is four half-lives), the fraction remaining is ${\left(\frac{1}{2}\right)}^{4}$ = $\frac{1}{16}$