Q: A laboratory technician needs to prepare 500 mL of a 0.250 M NaCl solution. How many grams of NaCl (molar mass = 58.44 g/mol) are required?

$$0.250 \times 0.500 \times 58.44 = 7.305 g$$

Q: If 100 mL of a 2.0 M HCl solution is diluted to a final volume of 500 mL, what is the new concentration?

$$2.0 \times \frac{100}{500} = 0.40 M$$

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

$$\frac{\text{mass of solute}}{\text{mass of solution}} \times 100$$

Q: A 250 mL solution contains 2.00 g of NaCl. What is the percent by mass of NaCl if the total mass of the solution is 252 g?

$$\frac{2.00}{252} \times 100 = 0.794\%$$

Q: How many milliliters of 6.0 M HCl are needed to prepare 250 mL of 1.5 M HCl by dilution?

$$V_1$$ = \frac{M_2V_2}{$$M_1$$} = \frac{1.5 \times 250}{6.0} = 62.5$$ mL

Q: A chemist mixes 100 mL of 0.10 M AgNO$$_3$$ with 100 mL of 0.10 M NaCl. What mass of AgCl (molar mass = 143.32 g/mol) will precipitate?

$$0.010 \text{ mol} \times 143.32 = 1.43 g$$

Q: Which of the following is the correct formula for calculating percent by volume?

$$\frac{\text{volume of solute}}{\text{volume of solution}} \times 100$$

Question 1

Which of the following best defines molarity ($$M) in a $$solution?

Accepted Answer

The number of moles of solute per liter of solution

Question 2

A laboratory technician needs to prepare 500 mL of a 0.250 M NaCl solution. How many grams of NaCl (molar mass = 58.44 g/mol) are required?

Accepted Answer

$$0.250 	imes 0.500 	imes 58.44 = 7.305 g$$

Question 3

Which equation is used to calculate the new concentration after dilution?

Accepted Answer

$$M_1V_1 = M_2V_2$$

Question 4

If 100 mL of a 2.0 M HCl solution is diluted to a final volume of 500 mL, what is the new concentration?

Accepted Answer

$$2.0 	imes \frac{100}{500} = 0.40 M$$

Question 5

A solution is prepared by dissolving 5.00 g of KNO$$_3 ($$molar mass = 101.1 g/mol) in enough water to make 250 mL of solution. What is the molarity?

Accepted Answer

$$\frac{5.00}{101.1} \div 0.250 = 0.198 M$$

Question 6

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

Accepted Answer

$$\frac{	ext{mass of solute}}{	ext{mass of solution}} 	imes 100$$

Question 7

A 250 mL solution contains 2.00 g of NaCl. What is the percent by mass of NaCl if the total mass of the solution is 252 g?

Accepted Answer

$$\frac{2.00}{252} 	imes 100 = 0.794\%$$

Question 8

Which of the following best describes a solution with a concentration of 1 ppm (parts per million)?

Accepted Answer

1 mg of solute per 1 kg of solution

Question 9

How many milliliters of 6.0 M HCl are needed to prepare 250 mL of 1.5 M HCl by dilution?

Accepted Answer

$$V_1$$ = \frac{M_2V_2}{$$M_1$$} = \frac{1.5 	imes 250}{6.0} = 62.5$$ mL

Question 10

A chemist mixes 100 mL of 0.10 M AgNO$$_3$$ with 100 mL of 0.10 M NaCl. What mass of AgCl (molar mass = 143.32 g/mol) will precipitate?

Accepted Answer

$$0.010 	ext{ mol} 	imes 143.32 = 1.43 g$$

Question 11

Which of the following is the correct formula for calculating percent by volume?

Accepted Answer

$$\frac{	ext{volume of solute}}{	ext{volume of solution}} 	imes 100$$

Question 12

A 0.500 L solution contains 0.0250 mol of glucose. What is the molarity of the solution?

Accepted Answer

$$\frac{0.0250}{0.500} = 0.0500 M$$

Question 13

Which of the following is a correct statement about solution stoichiometry?

Accepted Answer

It uses molarity and volume to relate reactants and products in a chemical reaction.

Question 14

A solution is labeled as 5.0% (w/v) NaCl. What does this mean?

Accepted Answer

5.0 g NaCl per 100 mL of solution

Question 15

If you have 250 mL of a 0.200 M solution, how many moles of solute are present?

Accepted Answer

$$0.200 	imes 0.250 = 0.050$$ mol

Question 16

Which of the following is the correct formula for parts per billion (ppb) by mass?

Accepted Answer

$$\frac{	ext{mass of solute}}{	ext{mass of solution}} 	imes 10^9$

Question 17

A 1.00 L solution contains 0.0050 g of lead(II) nitrate. What is the concentration in ppm?

Accepted Answer

$$\frac{0.0050}{1.00} 	imes 10^6$ = 5.0$$ ppm

Question 18

Which of the following is NOT a correct use of the dilution equation?

Accepted Answer

To find the mass of solute in a solution

Question 19

A 0.100 M solution of CaCl$$_2 is $$prepared by dissolving 1.11 g of CaCl$$_2 ($$molar mass = 110.98 g/mol) in water. What is the final volume of the solution?

Accepted Answer

$$\frac{1.11}{110.98} = 0.0100$$ mol; \quad V = \frac{0.0100}{0.100} = 0.100$ L

Solutions and Their Composition: Concentration, Dilution, and Percent Calculations

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