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

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