Q: Given the reaction $2A + B \rightarrow 3C$, which formula correctly expresses the rate in terms of the disappearance of $A$?

$\text{rate} = -\frac{1}{2} \frac{d[A]}{dt}$

Q: Which equation would you use to calculate the change in enthalpy for a reaction using standard enthalpies of formation?

$\Delta H^\circ_{\text{rxn}} = \sum \Delta H^\circ_{f,\text{products}} - \sum \Delta H^\circ_{f,\text{reactants}}$

Q: Which formula would you use to calculate the change in temperature when a known amount of heat is added to a substance of known mass and specific heat?

$q = c_s \times m \times \Delta T$

Q: Which of the following is the correct conversion factor for pressure from atm to Pa?

$1 \text{atm} = 101,300 \text{Pa}$

Q: A reaction has $E_a = 75 \mathrm{kJ/mol}$ and $A = 1.0 \times 10^{13} \mathrm{s}^{-1}$. What is the rate constant $k$ at $T = 298 \mathrm{K}$? ($R = 8.314 \mathrm{J/mol\cdot K}$)

$k \approx 1.6 \times 10^{-1} \mathrm{s}^{-1}$

Question 1

A sample of water is heated from 25°C to 75°C. If the mass of water is 100 g and the specific heat capacity $c$ is $4.18 \mathrm{J/g\cdot K}$, what is the amount of heat $q$ absorbed by the water?

Accepted Answer

$q = 20,900 \mathrm{J}$

Question 2

Which of the following correctly expresses the relationship between pressure, volume, and work done by a gas during expansion at constant pressure?

Accepted Answer

$w = -P \Delta V$

Question 3

Given the reaction $2A + B \rightarrow 3C$, which formula correctly expresses the rate in terms of the disappearance of $A$?

Accepted Answer

$	ext{rate} = -\frac{1}{2} \frac{d[A]}{dt}$

Question 4

A reaction has an activation energy $E_a$ of $50 \mathrm{kJ/mol}$. If the rate constant at $T_1 = 300 \mathrm{K}$ is $k_1 = 2.0 	imes 10^{-3} \mathrm{s}^{-1}$, what is the expected ratio $\frac{k_2}{k_1}$ at $T_2 = 350 \mathrm{K}$? (Use $R = 8.314 \mathrm{J/mol\cdot K}$)

Accepted Answer

$\frac{k_2}{k_1} \approx 5.4$

Question 5

Which equation would you use to calculate the change in enthalpy for a reaction using standard enthalpies of formation?

Accepted Answer

$\Delta H^\circ_{	ext{rxn}} = \sum \Delta H^\circ_{f,	ext{products}} - \sum \Delta H^\circ_{f,	ext{reactants}}$

Question 6

A 2.0 mol sample of an ideal gas expands isothermally at 1.0 atm from 10.0 L to 20.0 L. What is the work done by the gas? ($1 \mathrm{L\cdot atm} = 101.3 \mathrm{J}$)

Accepted Answer

$w = -1,400 \mathrm{J}$

Question 7

If the rate law for a reaction is $	ext{rate} = k[A][B]^2$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 8

Which of the following correctly expresses the relationship between the energy of a charged particle and the distance between charges?

Accepted Answer

$E_{el} = \frac{kQ_1Q_2}{d}$

Question 9

A first-order reaction has a rate constant $k = 0.693 \mathrm{min}^{-1}$. What is the half-life $t_{1/2}$ of the reaction?

Accepted Answer

$t_{1/2} = 1.0 \mathrm{min}$

Question 10

Which formula would you use to calculate the change in temperature when a known amount of heat is added to a substance of known mass and specific heat?

Accepted Answer

$q = c_s 	imes m 	imes \Delta T$

Question 11

For a reaction with two reactants $A$ and $B$, the rate law is $	ext{rate} = k[A]^2[B]$. If the concentration of $A$ is doubled and $B$ is tripled, by what factor does the rate increase?

Accepted Answer

The rate increases by a factor of 12.

Question 12

Which equation would you use to relate the rate constants of a reaction at two different temperatures?

Accepted Answer

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

Question 13

A reaction is found to be second order in $A$ and zero order in $B$. Which is the correct rate law?

Accepted Answer

$	ext{rate} = k[A]^2$

Question 14

Which of the following is the correct formula for the kinetic energy of a moving object?

Accepted Answer

$E_k = \frac{1}{2} m v^2$

Question 15

If the temperature of a system increases by 20°C, by how much does it increase in Kelvin?

Accepted Answer

20 K

Question 16

A reaction has a rate law $	ext{rate} = k[A]$. If $[A]_0 = 0.50 \mathrm{mol/L}$ and $k = 0.10 \mathrm{min}^{-1}$, what is $[A]$ after 10 minutes?

Accepted Answer

$[A] = 0.183 \mathrm{mol/L}$

Question 17

Which of the following is the correct conversion factor for pressure from atm to Pa?

Accepted Answer

$1 	ext{atm} = 101,300 	ext{Pa}$

Question 18

Which equation would you use to calculate the change in internal energy $\Delta E$ for a system where heat $q$ and work $w$ are known?

Accepted Answer

$\Delta E = q + w$

Question 19

A reaction has $E_a = 75 \mathrm{kJ/mol}$ and $A = 1.0 	imes 10^{13} \mathrm{s}^{-1}$. What is the rate constant $k$ at $T = 298 \mathrm{K}$? ($R = 8.314 \mathrm{J/mol\cdot K}$)

Accepted Answer

$k \approx 1.6 	imes 10^{-1} \mathrm{s}^{-1}$

General Chemistry: Essential Constants, Conversions, and Key Formulas

Study Guide - Practice Questions

Study Guide - Flashcards