Q: A student measures the mass of a liquid as 25.0 g and its volume as 10.0 mL. What is the density of the liquid, and which equation should be used?

Density $$= \frac{\text{mass}}{\text{volume}} = \frac{25.0\ \text{g}}{10.0\ \text{mL}} = 2.50\ \text{g/mL}$$

Q: A sample of gas at 1.00 atm and 300 K occupies 2.00 L. If the temperature is increased to 600 K at constant pressure, what will be the new volume? (Use Charles' Law: $$\frac{V_1$}{T_1$} = \frac{V_2$}{T_2$})$$

$$V_2$$ = \frac{$$V_1$$ \times $$T_2$$}{$$T_1$$} = \frac{2.00\ \text{L} \times 600\ \text{K}}{300\ \text{K}} = 4.00\ \text{L}$$

Q: A student mixes 50.0 mL of 1.0 M NaCl with 50.0 mL of 2.0 M NaCl. What is the final concentration of NaCl in the mixture? (Assume volumes are additive)

$$C_{final} = \frac{(1.0\ \text{M} \times 50.0\ \text{mL}) + (2.0\ \text{M} \times 50.0\ \text{mL})}{100.0\ \text{mL}} = 1.5\ \text{M}$$

Q: A reaction produces 5.0 g of product, but the theoretical yield is 6.0 g. What is the percent yield?

$$\text{Percent yield} = \frac{5.0\ \text{g}}{6.0\ \text{g}} \times 100\% = 83.3\%$$

Q: A solution is prepared by dissolving 10.0 g of NaOH (molar mass = 40.0 g/mol) in enough water to make 500.0 mL of solution. What is the molarity of the solution?

$$\text{Molarity} = \frac{\text{moles}}{\text{liters}} = \frac{\frac{10.0\ \text{g}}{40.0\ \text{g/mol}}}{0.500\ \text{L}} = 0.50\ \text{M}$$

Question 1

Which of the following best describes the particulate theory of matter?

Accepted Answer

Matter is composed of tiny, discrete particles that are in constant motion.

Question 2

A student measures the mass of a liquid as 25.0 g and its volume as 10.0 mL. What is the density of the liquid, and which equation should be used?

Accepted Answer

Density $$= \frac{	ext{mass}}{	ext{volume}} = \frac{25.0\ 	ext{g}}{10.0\ 	ext{mL}} = 2.50\ 	ext{g/mL}$$

Question 3

Which of the following is an example of a physical change?

Accepted Answer

Dissolving sugar in water.

Question 4

A sample of gas at 1.00 atm and 300 K occupies 2.00 L. If the temperature is increased to 600 K at constant pressure, what will be the new volume? (Use Charles' Law: $$\frac{V_1$}{T_1$} = \frac{V_2$}{T_2$})$$

Accepted Answer

$$V_2$$ = \frac{$$V_1$$ 	imes $$T_2$$}{$$T_1$$} = \frac{2.00\ 	ext{L} 	imes 600\ 	ext{K}}{300\ 	ext{K}} = 4.00\ 	ext{L}$$

Question 5

Which statement about the atomic theory of matter is correct?

Accepted Answer

Atoms of the same element have identical properties.

Question 6

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

Accepted Answer

CH$$_2O$$

Question 7

Which of the following best explains why water boils at a lower temperature at high altitude?

Accepted Answer

The atmospheric pressure is lower, so the vapor pressure required for boiling is reached at a lower temperature.

Question 8

Which equation correctly relates the number of moles, mass, and molar mass of a substance?

Accepted Answer

$$n = \frac{m}{M}$$

Question 9

A student mixes 50.0 mL of 1.0 M NaCl with 50.0 mL of 2.0 M NaCl. What is the final concentration of NaCl in the mixture? (Assume volumes are additive)

Accepted Answer

$$C_{final} = \frac{(1.0\ 	ext{M} 	imes 50.0\ 	ext{mL}) + (2.0\ 	ext{M} 	imes 50.0\ 	ext{mL})}{100.0\ 	ext{mL}} = 1.5\ 	ext{M}$$

Question 10

Which of the following is a chemical property?

Accepted Answer

Reactivity with acid

Question 11

A reaction produces 5.0 g of product, but the theoretical yield is 6.0 g. What is the percent yield?

Accepted Answer

$$	ext{Percent yield} = \frac{5.0\ 	ext{g}}{6.0\ 	ext{g}} 	imes 100\% = 83.3\%$$

Question 12

Which statement about intermolecular forces is correct?

Accepted Answer

London dispersion forces are present in all molecules, regardless of polarity.

Question 13

Which of the following best describes the difference between empirical and molecular formulas?

Accepted Answer

Empirical formulas show the simplest whole-number ratio of atoms; molecular formulas show the actual number of atoms in a molecule.

Question 14

A solution is prepared by dissolving 10.0 g of NaOH (molar mass = 40.0 g/mol) in enough water to make 500.0 mL of solution. What is the molarity of the solution?

Accepted Answer

$$	ext{Molarity} = \frac{	ext{moles}}{	ext{liters}} = \frac{\frac{10.0\ 	ext{g}}{40.0\ 	ext{g/mol}}}{0.500\ 	ext{L}} = 0.50\ 	ext{M}$$

Question 15

Which of the following is NOT a postulate of Dalton's atomic theory?

Accepted Answer

Atoms can be subdivided, created, or destroyed in chemical reactions.

Question 16

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed.

Question 17

Which equation is used to calculate the energy of a photon given its frequency? (Planck's equation)

Accepted Answer

$$E = h 
u$$

Question 18

A student needs to prepare 250.0 mL of 0.10 M HCl from a stock solution of 1.0 M HCl. What volume of stock solution is required? (Use $$M_1V_1 = M_2V_2)$$

Accepted Answer

$$V_1$$ = \frac{M_2V_2}{$$M_1$$} = \frac{0.10\ 	ext{M} 	imes 250.0\ 	ext{mL}}{1.0\ 	ext{M}} = 25.0\ 	ext{mL}$$

Question 19

Which statement about solution concentration is correct?

Accepted Answer

A 1.0 M solution contains 1.0 mole of solute per liter of solution.

Introductory Chemistry 22: Course Structure, Topics, and Study Guide

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