Q: A sample of gas in a sealed syringe has a volume of 40.0 mL at a pressure of 1.00 atm. If the pressure is increased to 2.50 atm at constant temperature, what is the new volume of the gas?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 \times 40.0}{2.50} = 16.0\ \mathrm{mL}$$

Q: A 5.00 L tank contains oxygen gas at 2.00 atm and 300 K. How many moles of oxygen are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

$$n = \frac{PV}{RT} = \frac{2.00 \times 5.00}{0.0821 \times 300} = 0.406\ \mathrm{mol}$$

Q: A mixture of gases contains 70% nitrogen, 20% oxygen, and 10% argon by volume at a total pressure of 1.00 atm. What is the partial pressure of oxygen?

$$P_{O_2$} = 0.20 \times 1.00 = 0.20\ \mathrm{atm}$$

Q: A 0.300 mol sample of naphthalene (molar mass = 128 g/mol) requires 19.0 kJ/mol to melt. How much heat is required to melt the sample?

$$q = n \times \Delta H_{fus} = 0.300 \times 19.0 = 5.7\ \mathrm{kJ}$$

Question 1

Which of the following phase changes is exothermic and results in a decrease in entropy?

Accepted Answer

Freezing of liquid water to ice

Question 2

A sample of gas in a sealed syringe has a volume of 40.0 mL at a pressure of 1.00 atm. If the pressure is increased to 2.50 atm at constant temperature, what is the new volume of the gas?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 	imes 40.0}{2.50} = 16.0\ \mathrm{mL}$$

Question 3

Which of the following substances would you expect to have the highest boiling point, and why?

Accepted Answer

Acetic acid ($$\mathrm{CH_3COOH}$$), because it has hydrogen bonding, dipole-dipole, and London dispersion forces

Question 4

A 2.0 L sample of gas at 300 K and 1.0 atm is compressed to 1.0 L and heated to 600 K. What is the final pressure of the gas?

Accepted Answer

$$P_2$$ = \frac{$$P_1$$ $$V_1$$ $$T_2$$}{$$T_1$$ $$V_2$$} = \frac{1.0 	imes 2.0 	imes 600}{300 	imes 1.0} = 4.0\ \mathrm{atm}$$

Question 5

Which of the following best explains why water has a much higher boiling point than hydrogen sulfide ($$\mathrm{H_2S}$$)?

Accepted Answer

Water molecules form hydrogen bonds, which are much stronger than the dipole-dipole forces in $$\mathrm{H_2S}.$$

Question 6

A 5.00 L tank contains oxygen gas at 2.00 atm and 300 K. How many moles of oxygen are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$n = \frac{PV}{RT} = \frac{2.00 	imes 5.00}{0.0821 	imes 300} = 0.406\ \mathrm{mol}$$

Question 7

Which of the following statements about crystalline and amorphous solids is correct?

Accepted Answer

Crystalline solids have a regular, repeating structure, while amorphous solids lack long-range order.

Question 8

A mixture of gases contains 70% nitrogen, 20% oxygen, and 10% argon by volume at a total pressure of 1.00 atm. What is the partial pressure of oxygen?

Accepted Answer

$$P_{O_2$} = 0.20 	imes 1.00 = 0.20\ \mathrm{atm}$$

Question 9

Which of the following best describes the behavior of an ideal gas according to the kinetic-molecular theory?

Accepted Answer

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

Question 10

A 0.300 mol sample of naphthalene (molar mass = 128 g/mol) requires 19.0 kJ/mol to melt. How much heat is required to melt the sample?

Accepted Answer

$$q = n 	imes \Delta H_{fus} = 0.300 	imes 19.0 = 5.7\ \mathrm{kJ}$$

Question 11

Which of the following liquids would you expect to have the highest surface tension?

Accepted Answer

A liquid with strong hydrogen bonding

Question 12

A balloon filled with 2.00 mol of helium at 1.00 atm and 273 K has a volume of 44.8 L. If the amount of helium is doubled at constant temperature and pressure, what will be the new volume?

Accepted Answer

89.6 L

Question 13

Which of the following best explains why metals are malleable and conduct electricity?

Accepted Answer

Metals have a sea of delocalized electrons that can move freely.

Question 14

A sample of gas occupies 500 mL at 27°C and 1.00 atm. What will be its volume at 127°C and 1.00 atm?

Accepted Answer

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 500 	imes \frac{400}{300} = 667\ \mathrm{mL}$$

Question 15

Which of the following statements about vapor pressure is correct?

Accepted Answer

Vapor pressure increases with increasing temperature and is higher for liquids with weaker intermolecular forces.

Question 16

A steel cylinder contains 5.54 kg of methane ($$\mathrm{CH_4$}$$, molar mass = 16.0 g/mol) in a 43.8 L volume at 20.0°C. What is the pressure inside the cylinder? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$n = \frac{5540}{16.0} = 346.25\ \mathrm{mol};\ T = 293\ \mathrm{K};\ P = \frac{nRT}{V} = \frac{346.25 	imes 0.0821 	imes 293}{43.8} = 190\ \mathrm{atm}$$

Question 17

Which of the following is NOT a type of intermolecular force?

Accepted Answer

Ionic bond

Gases, Liquids, and Solids: States of Matter and Their Properties

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