Q: A sample of gas occupies 2.50 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 300 K, assuming ideal gas behavior?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 \times 2.50}{2.00} = 1.25\ \text{L}$$

Q: A mixture of gases contains 2.0 mol of O$$_2$$, 1.0 mol of N$$_2$$, and 1.0 mol of CO$$_2 in a 10.0 L $$container at 300 K. What is the partial pressure of O$$_2$$? (Use $$R = 0.0821\ \text{L atm mol}^{-1}\text{K}^{-1})$$

$$P_{O_2$} = \frac{nRT}{V} = \frac{2.0 \times 0.0821 \times 300}{10.0} = 4.93\ \text{atm}$$

Q: A solution is prepared by dissolving 0.50 mol of NaCl in enough water to make 1.0 L of solution. What is the molarity of the solution?

$$M = \frac{0.50\ \text{mol}}{1.0\ \text{L}} = 0.50\ \text{M}$$

Q: A 5.0 L container holds a mixture of 1.0 mol He and 2.0 mol Ar at 400 K. What is the total pressure in the container? ($$R = 0.0821\ \text{L atm mol}^{-1}\text{K}^{-1})$$

$$P_{total} = \frac{(1.0 + 2.0) \times 0.0821 \times 400}{5.0} = 19.7\ \text{atm}$$

Question 1

Which of the following statements best describes the difference between intermolecular and intramolecular forces?

Accepted Answer

Intermolecular forces occur between molecules and influence physical properties like boiling point, while intramolecular forces hold atoms together within a molecule.

Question 2

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 300 K, assuming ideal gas behavior?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 	imes 2.50}{2.00} = 1.25\ 	ext{L}$$

Question 3

Which of the following best explains why water has a higher boiling point than methane?

Accepted Answer

Water forms hydrogen bonds, which are stronger than the London dispersion forces present in methane.

Question 4

Which equation correctly relates the pressure, volume, and temperature of an ideal gas?

Accepted Answer

$$PV = nRT$$

Question 5

A mixture of gases contains 2.0 mol of O$$_2$$, 1.0 mol of N$$_2$$, and 1.0 mol of CO$$_2 in a 10.0 L $$container at 300 K. What is the partial pressure of O$$_2$$? (Use $$R = 0.0821\ 	ext{L atm mol}^{-1}	ext{K}^{-1})$$

Accepted Answer

$$P_{O_2$} = \frac{nRT}{V} = \frac{2.0 	imes 0.0821 	imes 300}{10.0} = 4.93\ 	ext{atm}$$

Question 6

According to kinetic molecular theory, which of the following statements is true for an ideal gas?

Accepted Answer

The average kinetic energy of gas particles is proportional to the temperature in Kelvin.

Question 7

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

Accepted Answer

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

Question 8

Which of the following best describes the effect of increasing temperature on the solubility of most solids in water?

Accepted Answer

Solubility increases as temperature increases.

Question 9

A solution is prepared by dissolving 0.50 mol of NaCl in enough water to make 1.0 L of solution. What is the molarity of the solution?

Accepted Answer

$$M = \frac{0.50\ 	ext{mol}}{1.0\ 	ext{L}} = 0.50\ 	ext{M}$$

Question 10

Which of the following equations is used to calculate the absorbance ($$A) of a $$solution in spectrophotometry?

Accepted Answer

$$A = \varepsilon c l$$

Question 11

Which of the following best describes the relationship between pressure and volume for a gas at constant temperature?

Accepted Answer

Pressure and volume are inversely proportional.

Question 12

A 5.0 L container holds a mixture of 1.0 mol He and 2.0 mol Ar at 400 K. What is the total pressure in the container? ($$R = 0.0821\ 	ext{L atm mol}^{-1}	ext{K}^{-1})$$

Accepted Answer

$$P_{total} = \frac{(1.0 + 2.0) 	imes 0.0821 	imes 400}{5.0} = 19.7\ 	ext{atm}$$

Question 13

Which of the following is NOT a postulate of the kinetic molecular theory?

Accepted Answer

Gas particles exert attractive forces on each other.

Question 14

Which of the following best explains why real gases deviate from ideal behavior at high pressures?

Accepted Answer

The volume of gas particles becomes significant compared to the container volume.

Question 15

Which of the following is the correct expression for the equilibrium constant ($$K) $$for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 16

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst increases the rate of reaction by lowering the activation energy.

Question 17

Which of the following is the correct formula for calculating the molality ($$m) of a $$solution?

Accepted Answer

$$m = \frac{	ext{moles of solute}}{	ext{kg of solvent}}$$

Question 18

Which of the following best describes the relationship between absorbance and concentration in spectrophotometry?

Accepted Answer

Absorbance is directly proportional to concentration.

Question 19

Which of the following best explains the photoelectric effect?

Accepted Answer

Electrons are emitted from a metal surface when it is exposed to light of sufficient frequency.

Unit 3 Study Guide: Molecules, Gases, Solutions, and Spectroscopy

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