Q: A sample of gas occupies 12.0 L at 2.00 atm and 300 K. If the pressure is decreased to 1.00 atm and the temperature is increased to 400 K, what will be the new volume of the gas (assume n is constant)?

$$V_2$$ = $$V_1$$ \times \frac{$$P_1$$}{$$P_2$$} \times \frac{$$T_2$$}{$$T_1$$} = 12.0 \times \frac{2.00}{1.00} \times \frac{400}{300} = 32.0\ \mathrm{L}$$

Q: A reaction has a rate law: $$\text{Rate} = k[NO_2$]^2[CO]. If $$the concentration of NO$$_2 is $$doubled and CO is tripled, by what factor does the rate increase?

Rate increases by $$2^2$$ \times 3 = 12$$ times.

Q: A first-order reaction has a half-life of 10.0 minutes. How long will it take for 75% of the reactant to be consumed?

$$t = 2 \times t_{1/2} = 20.0\ \mathrm{min}$$

Question 1

A sample of gas occupies 12.0 L at 2.00 atm and 300 K. If the pressure is decreased to 1.00 atm and the temperature is increased to 400 K, what will be the new volume of the gas (assume n is constant)?

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \frac{$$P_1$$}{$$P_2$$} 	imes \frac{$$T_2$$}{$$T_1$$} = 12.0 	imes \frac{2.00}{1.00} 	imes \frac{400}{300} = 32.0\ \mathrm{L}$$

Question 2

Which of the following statements about intermolecular forces is TRUE?

Accepted Answer

Ion-dipole forces are stronger than hydrogen bonds.

Question 3

A 0.250 mol sample of an unknown gas has a mass of 7.00 g and occupies 5.00 L at 350 K. What is the identity of the gas?

Accepted Answer

The molar mass is $$M = \frac{7.00\ \mathrm{g}}{0.250\ \mathrm{mol}} = 28.0\ \mathrm{g/mol}$$, which matches N$$_2.$$

Question 4

Which of the following molecules can form hydrogen bonds with itself?

Accepted Answer

CH$$_3OH ($$methanol)

Question 5

A mixture contains 2.0 mol Ar, 1.0 mol N$$_2$$, and 3.0 mol SO$$_2 at a $$total pressure of 10.0 atm. What is the partial pressure of SO$$_2$$?

Accepted Answer

$$X_{SO_2$} = \frac{3.0}{2.0+1.0+3.0} = 0.5;\ P_{SO_2$} = 0.5 	imes 10.0 = 5.0\ \mathrm{atm}$$

Question 6

Which of the following best explains why ice floats on liquid water?

Accepted Answer

The hydrogen-bonded network in ice holds water molecules farther apart, making ice less dense than liquid water.

Question 7

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 8

A reaction has a rate law: $$	ext{Rate} = k[NO_2$]^2[CO]. If $$the concentration of NO$$_2 is $$doubled and CO is tripled, by what factor does the rate increase?

Accepted Answer

Rate increases by $$2^2$$ 	imes 3 = 12$$ times.

Question 9

Which of the following statements about the Maxwell-Boltzmann distribution is correct?

Accepted Answer

At the same temperature, a lighter gas will have a distribution curve shifted to higher speeds compared to a heavier gas.

Question 10

Which of the following best describes the effect of increasing temperature on the vapor pressure of a liquid?

Accepted Answer

Vapor pressure increases exponentially with temperature.

Question 11

A first-order reaction has a half-life of 10.0 minutes. How long will it take for 75% of the reactant to be consumed?

Accepted Answer

$$t = 2 	imes t_{1/2} = 20.0\ \mathrm{min}$$

Question 12

Which of the following molecules has the highest boiling point?

Accepted Answer

CH$$_3OH ($$methanol)

Question 13

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

Accepted Answer

$$\frac{1}{[A]} = kt + \frac{1}{[A]_0}$$

Question 14

Which of the following best explains why n-pentane has a higher boiling point than neopentane, even though they have the same molecular formula?

Accepted Answer

n-Pentane has a larger surface area, leading to stronger dispersion forces.

Question 15

A sample of water is heated from $$-10\ ^\circ\mathrm{C} to$$ $$110\ ^\circ\mathrm{C}. $$Which equation would you use to calculate the heat required to melt the ice at $$0\ ^\circ\mathrm{C}$$?

Accepted Answer

$$q = n \cdot \Delta H_{fus}$$

Question 16

Which of the following is the correct Clausius–Clapeyron equation for calculating the vapor pressure at a new temperature?

Accepted Answer

$$\ln\left(\frac{P_2$}{P_1$}\right) = -\frac{\Delta H_{vap}}{R}\left(\frac{1}{T_2$} - \frac{1}{T_1$}\right)$$

Question 17

Which of the following is TRUE about the rate constant $$k$$ for a first-order reaction?

Accepted Answer

The units of $$k$$ are $$\mathrm{s}^{-1}.$$

Question 18

Which of the following best describes the effect of increasing intermolecular forces on the properties of a liquid?

Accepted Answer

Higher boiling point, higher viscosity, higher surface tension, lower vapor pressure.

Question 19

Which of the following is the correct expression for the root-mean-square speed ($$u_{rms}) of a $$gas molecule?

Accepted Answer

$$u_{rms} = \sqrt{\frac{3RT}{M}}$$

General Chemistry Study Guide: Gases, Liquids & Phase Changes, and Kinetics

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