Q: A sample of gas occupies 4.0 L at 1.0 atm and 300 K. What will be its volume at 2.0 atm and 300 K, assuming the amount of gas remains constant?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.0 \times 4.0}{2.0} = 2.0\ \text{L}$$

Q: A 0.50 M NaCl solution is prepared by dissolving NaCl in water to make 250 mL of solution. How many moles of NaCl are present?

$$n = M \times V = 0.50 \times 0.250 = 0.125\ \text{mol}$$

Q: A solution is prepared by dissolving 10.0 g of glucose (C$$_6H$_{12}O$_6) in $$enough water to make 500.0 g of solution. What is the mass percent of glucose in the solution?

$$\text{Mass percent} = \frac{10.0}{500.0} \times 100\% = 2.0\%$$

Q: A 2.0 L container holds a mixture of N$$_2 at 0.50 $$atm and O$$_2 at 0.75 $$atm. What is the total pressure according to Dalton’s Law of Partial Pressures?

$$P_{\text{total}} = 0.50 + 0.75 = 1.25\ \text{atm}$$

Q: A gas is collected over water at 25$$^\circC. $$The total pressure is 760 mmHg, and the vapor pressure of water at this temperature is 24 mmHg. What is the pressure of the dry gas?

$$P_{\text{gas}} = 760 - 24 = 736\ \text{mmHg}$$

Question 1

Which of the following molecules violates the octet rule when drawing its Lewis structure?

Accepted Answer

BF$$_3$$

Question 2

Which of the following best describes the geometry of a molecule with three electron groups around the central atom according to VSEPR theory?

Accepted Answer

Trigonal planar

Question 3

A sample of gas occupies 4.0 L at 1.0 atm and 300 K. What will be its volume at 2.0 atm and 300 K, assuming the amount of gas remains constant?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.0 	imes 4.0}{2.0} = 2.0\ 	ext{L}$$

Question 4

Which of the following statements about resonance structures is correct?

Accepted Answer

The actual structure is a hybrid of all resonance forms.

Question 5

Which of the following pairs of atoms will form a polar covalent bond?

Accepted Answer

C and O

Question 6

A 0.50 M NaCl solution is prepared by dissolving NaCl in water to make 250 mL of solution. How many moles of NaCl are present?

Accepted Answer

$$n = M 	imes V = 0.50 	imes 0.250 = 0.125\ 	ext{mol}$$

Question 7

Which of the following gases will have the highest rate of effusion under identical conditions?

Accepted Answer

NH$$_3$$

Question 8

A solution is prepared by dissolving 10.0 g of glucose (C$$_6H$_{12}O$_6) in $$enough water to make 500.0 g of solution. What is the mass percent of glucose in the solution?

Accepted Answer

$$	ext{Mass percent} = \frac{10.0}{500.0} 	imes 100\% = 2.0\%$$

Question 9

Which of the following statements about electrolytes is true?

Accepted Answer

Strong electrolytes completely dissociate into ions in water.

Question 10

A 2.0 L container holds a mixture of N$$_2 at 0.50 $$atm and O$$_2 at 0.75 $$atm. What is the total pressure according to Dalton’s Law of Partial Pressures?

Accepted Answer

$$P_{	ext{total}} = 0.50 + 0.75 = 1.25\ 	ext{atm}$$

Question 11

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

It has polar bonds and a bent molecular geometry.

Question 12

A gas is collected over water at 25$$^\circC. $$The total pressure is 760 mmHg, and the vapor pressure of water at this temperature is 24 mmHg. What is the pressure of the dry gas?

Accepted Answer

$$P_{	ext{gas}} = 760 - 24 = 736\ 	ext{mmHg}$$

Question 13

Which of the following is the correct Lewis structure for the ammonium ion (NH$$_4^+$$)?

Accepted Answer

N with four single bonds to H, and a positive charge on the N

Question 14

A 1.0 M solution of HCl is diluted to make 0.25 M solution. If the final volume is 200 mL, what was the initial volume of the 1.0 M solution used?

Accepted Answer

$$M_1$$ $$V_1$$ = $$M_2$$ $$V_2$$ \Rightarrow $$V_1$$ = \frac{$$M_2$$ $$V_2$$}{$$M_1$$} = \frac{0.25 	imes 200}{1.0} = 50\ 	ext{mL}$$

Question 15

Which of the following is the correct expression for the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 16

What is the molarity of a solution prepared by dissolving 5.85 g of NaCl (molar mass = 58.5 g/mol) in enough water to make 0.500 L of solution?

Accepted Answer

$$M = \frac{n}{V} = \frac{5.85/58.5}{0.500} = 0.2\ 	ext{M}$$

Question 17

Which of the following best describes the difference between ionic and covalent Lewis structures?

Accepted Answer

Ionic Lewis structures show electron transfer; covalent show electron sharing.

Question 18

A 1.00 L sample of gas at STP contains how many moles of gas? (STP: 1 atm, 273 K, 22.4 L/mol)

Accepted Answer

$$n = \frac{1.00}{22.4} = 0.0446\ 	ext{mol}$$

Question 19

Which of the following is a nonelectrolyte solution?

Accepted Answer

A solution of sugar (C$$_6H$_{12}O$_6) in $$water

Question 20

Which of the following best describes the relationship between temperature and volume for a gas at constant pressure (Charles’s Law)?

Accepted Answer

Volume is directly proportional to temperature in Kelvin.

Study Notes: Chemical Bonding, Gases, and Solutions (Chapters 10, 11, 13)

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