Q: A sample of gas occupies 5.31 L at 372 K and 1.25 atm. What is the pressure of this gas when the volume is expanded to 8.33 L at a temperature of 398 K?

$P_2 = \frac{P_1 V_1 T_2}{T_1 V_2} = \frac{1.25 \times 5.31 \times 398}{372 \times 8.33} = 0.85\ \text{atm}$

Q: A 12.0 L cylinder contains gas at 29.8 atm. If the gas is transferred to a 0.80 L cylinder at the same temperature, what is the new pressure?

$P_2 = \frac{P_1 V_1}{V_2} = \frac{29.8 \times 12.0}{0.80} = 447\ \text{atm}$

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

$P = \frac{nRT}{V} = \frac{4.0 \times 0.0821 \times 300}{10.0} = 9.85\ \text{atm}$

Q: Which of the following is the correct formula for percent composition by mass?

$\%\ \text{composition} = \frac{\text{mass of element}}{\text{total mass of compound}} \times 100$

Question 1

A sample of gas occupies 5.31 L at 372 K and 1.25 atm. What is the pressure of this gas when the volume is expanded to 8.33 L at a temperature of 398 K?

Accepted Answer

$P_2 = \frac{P_1 V_1 T_2}{T_1 V_2} = \frac{1.25 	imes 5.31 	imes 398}{372 	imes 8.33} = 0.85\ 	ext{atm}$

Question 2

Which of the following statements best describes the relationship between intermolecular forces and boiling point?

Accepted Answer

Stronger intermolecular forces result in a higher boiling point because more energy is required to separate the molecules.

Question 3

A 12.0 L cylinder contains gas at 29.8 atm. If the gas is transferred to a 0.80 L cylinder at the same temperature, what is the new pressure?

Accepted Answer

$P_2 = \frac{P_1 V_1}{V_2} = \frac{29.8 	imes 12.0}{0.80} = 447\ 	ext{atm}$

Question 4

Which of the following molecules is expected to have the highest dipole moment?

Accepted Answer

HCl

Question 5

Which of the following is NOT a valid assumption of the kinetic molecular theory of gases?

Accepted Answer

Gas particles exert attractive and repulsive forces on each other.

Question 6

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula?

Accepted Answer

CH$_2$O

Question 7

Which of the following best explains why water (H$_2$O) has a higher boiling point than methane (CH$_4$)?

Accepted Answer

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

Question 8

Which of the following is the correct formula for calculating the density of a gas using the ideal gas law?

Accepted Answer

$d = \frac{PM}{RT}$

Question 9

Which statement about London dispersion forces is correct?

Accepted Answer

They are present in all molecules, but are the only intermolecular force in nonpolar molecules.

Question 10

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

Accepted Answer

$P = \frac{nRT}{V} = \frac{4.0 	imes 0.0821 	imes 300}{10.0} = 9.85\ 	ext{atm}$

Question 11

Which of the following molecules is nonpolar despite having polar bonds?

Accepted Answer

CO$_2$

Question 12

Which of the following is the correct Lewis structure for ammonia (NH$_3$)?

Accepted Answer

A nitrogen atom with three single bonds to hydrogen atoms and one lone pair on nitrogen.

Question 13

Which of the following best describes the effect of increasing temperature on the average kinetic energy of gas molecules?

Accepted Answer

The average kinetic energy increases proportionally with temperature.

Question 14

Which of the following is the correct formula for percent composition by mass?

Accepted Answer

$\%\ 	ext{composition} = \frac{	ext{mass of element}}{	ext{total mass of compound}} 	imes 100$

Question 15

Which of the following gases will effuse the fastest under identical conditions?

Accepted Answer

H$_2$

Question 16

Which of the following is the correct relationship for Boyle's Law?

Accepted Answer

$P_1 V_1 = P_2 V_2$

Question 17

A gas sample at 1.00 atm and 273 K occupies 22.4 L. What is the molar mass of the gas if 44.8 g is present?

Accepted Answer

$M = \frac{	ext{mass}}{	ext{moles}} = \frac{44.8}{1.0} = 44.8\ 	ext{g/mol}$

Question 18

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

Strong electrostatic forces between oppositely charged ions require a large amount of energy to break.

Question 19

Which of the following is the correct formula for calculating the partial pressure of a gas in a mixture?

Accepted Answer

$P_A = X_A P_{	ext{total}}$

General Chemistry Exam 2 Study Guide: Chapters 5, 6, and 8

Study Guide - Practice Questions

Study Guide - Flashcards