# General Chemistry 2: Rates of Reaction

Consider a solution of 0.10 M H$^{+}$ in 0.10 M thioacetimide at 25 $^\circ$C

rate = k[H$^{+}$][CH$_3$CSNH$_2$]

How are the rate and the rate constant (k) effected when water is added to the solution? When the reaction is heated to 75$^\circ$C ? When NaOH is added?

The initial concentration of hydroiodic acid is 100 mmol/L but after 500 s it is 17 mmol/L. What is the rate? (note the products of this reaction are hydrogen and iodine gas)

The following initial rate data was collected for the reaction, A + 2B $\longrightarrow$ products

B. Find the rate constant

The following initial rate data was collected for the reaction, 2 NO + O$_2$ $\longrightarrow$ 2NO$_2$

[NO$_2$]$^X$[O$_2$]$^Y$

The following initial rate data was collected for the reaction, CH$_3$Br + OH$^-$ $\longrightarrow$ CH$_3$OH + Br$^-$

B. What is the rate constant?

The following initial rate data was collected for the reaction, A + B + C $\longrightarrow$ products

What are the reaction orders with respect to the reactants?

When cyclopropane is heated to 500 $^\circ$C it changes to propene. The following data was obtained from experiment:

Confirm that the reaction is 1st order and calculate the rate constant.

An isotope of phosphorous, $^{32}$P, is radioactive and undergoes beta decay with a half life of 14.3 days. How long would it take for 99% of a sample of this isotope to decay?

A $\longrightarrow$ products

t$_\frac{1}{2}$ = 180s

A. What % of A is left unreacted at 900 s?

B. What is the rate at [A] = 0.50 M?

The half life of uranium-238 is 4.51 x 10$^9$ years. What is the rate constant? How much uranium-238 is left after 4 half lives if we start with 64 mg?

A first order reaction has a half life of 20.0 min.

A. Calculate the rate constant for this reaction

B. How much time is required for this reaction to be 75% complete?

For a given reaction, the reaction rate exactly doubles when the temperature is raised from 293 K to 304 K. Calculate the activation energy.

Below is a proposed mechanism for a reaction, with k2 > k1. What is the rate law?

$NO_2 + CO~ \xrightarrow{k_1}~ NO + NO_3$

$NO_3 + CO~ \xrightarrow{k_2}~ NO_2 + CO_2$

Below is a proposed mechanism for a reaction, with k1 > k2. What is the rate law?

$NO_2 + CO~ \xrightarrow{k_1}~ NO + NO_3$

$NO_3 + CO~ \xrightarrow{k_2}~ NO_2 + CO_2$

Below is a proposed mechanism for a reaction, with k1 > k2. What is the rate law?

$NO+ Br_2~ \mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~ NOBr_2$

$NOBr_2 + NO~ \xrightarrow{k_2}~ NOBr + NOBr$

For the mechanism proposed below, determine the overall rate law for k$_1$ < k$_2$, k$_1$ > k$_2$

$2~NO~+~2 H_2~\longrightarrow~2~H_2O~+~N_2~~{overall}$

$2~NO+~H_2~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~N_2O~+~H_2O$

$N_2O~+~H_2~\xrightarrow{k_2}~N_2~+~H_2O$

For the mechanism proposed below, use the quasi (pseudo) steady state approximation to determine the overall rate law assuming the pseudo steady state.

$2~NO~+~2 H_2~\longrightarrow~2~H_2O~+~N_2~~{overall}$

$2~NO+~H_2~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~N_2O~+~H_2O$

$N_2O~+~H_2~\xrightarrow{k_2}~N_2~+~H_2O$

For the mechanism below, determine the overall rate law.

$2~NO~+~Br_2~\longrightarrow~2~NOBr~~{overall}$

$NO+~Br_2~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~NOBr_2$

$NOBr_2~+~NO~\xrightarrow{k_2}~2NOBr$

Derive the rate law given the elementary steps.

$Cl_2~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~2~Cl~~{1}$

$Cl+~CHCl_3~\xrightarrow{k_2}~HCl~+~CCl_3~~{2}$

$Cl~+~CCl_3~\xrightarrow{k_3}~CCl_4~~{3}$

Use the pseudo steady state hypothesis to derive the rate law for the rate of production of P

$E~+~S~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~ES$

$ES~\xrightarrow{k_2}~E~+P$