Q: A student needs to prepare 250.0 mL of a 0.2500 M K$$_2$$CrO$$_4$$ solution. The molar mass of K$$_2$$CrO$$_4 is 194.1903 g/$$mol. How many grams of K$$_2$$CrO$$_4$$ are required?

$$0.2500\ \text{L} \times 0.2500\ \text{mol/L} \times 194.1903\ \text{g/mol} = 12.14\ \text{g}$$

Q: What is the molarity of a solution prepared by dissolving 0.110 moles of urea in enough water to make 250.0 mL of solution?

$$M = \frac{0.110\ \text{mol}}{0.2500\ \text{L}} = 0.440\ \text{M}$$

Q: A laboratory technician needs to dilute 15.00 mL of 0.450 M K$$_2$$CrO$$_4 to a $$final volume of 100.0 mL. What is the new concentration?

$$M_2$$ = \frac{15.00\ \text{mL} \times 0.450\ \text{M}}{100.0\ \text{mL}} = 0.0675\ \text{M}$$

Q: A solution is prepared by adding 25.00 mL of ethanol (density = 0.789 g/mL, MM = 46.0688 g/mol) to enough water to make 250.0 mL of solution. What is the molarity of ethanol in the solution?

$$M = \frac{25.00\ \text{mL} \times 0.789\ \text{g/mL} \times \frac{1\ \text{mol}}{46.0688\ \text{g}}}{0.2500\ \text{L}} = 1.71\ \text{M}$$

Q: A stock solution of HCl has a concentration of 12.8 M. What volume of this stock solution is required to prepare 250.0 mL of 0.1000 M HCl?

$$V_1$$ = \frac{0.1000\ \text{M} \times 250.0\ \text{mL}}{12.8\ \text{M}} = 1.95\ \text{mL}$$

Question 1

Which of the following best describes a solution in chemistry?

Accepted Answer

A mixture of two or more substances with variable proportions that is homogeneous throughout.

Question 2

A student needs to prepare 250.0 mL of a 0.2500 M K$$_2$$CrO$$_4$$ solution. The molar mass of K$$_2$$CrO$$_4 is 194.1903 g/$$mol. How many grams of K$$_2$$CrO$$_4$$ are required?

Accepted Answer

$$0.2500\ 	ext{L} 	imes 0.2500\ 	ext{mol/L} 	imes 194.1903\ 	ext{g/mol} = 12.14\ 	ext{g}$$

Question 3

Which statement about solvents and solutes is correct?

Accepted Answer

The solvent is present in the greatest amount and determines the state of the solution.

Question 4

What is the molarity of a solution prepared by dissolving 0.110 moles of urea in enough water to make 250.0 mL of solution?

Accepted Answer

$$M = \frac{0.110\ 	ext{mol}}{0.2500\ 	ext{L}} = 0.440\ 	ext{M}$$

Question 5

A laboratory technician needs to dilute 15.00 mL of 0.450 M K$$_2$$CrO$$_4 to a $$final volume of 100.0 mL. What is the new concentration?

Accepted Answer

$$M_2$$ = \frac{15.00\ 	ext{mL} 	imes 0.450\ 	ext{M}}{100.0\ 	ext{mL}} = 0.0675\ 	ext{M}$$

Question 6

Which of the following is NOT a correct statement about molarity?

Accepted Answer

Molarity is defined as moles of solute per kilogram of solvent.

Question 7

A solution is prepared by adding 25.00 mL of ethanol (density = 0.789 g/mL, MM = 46.0688 g/mol) to enough water to make 250.0 mL of solution. What is the molarity of ethanol in the solution?

Accepted Answer

$$M = \frac{25.00\ 	ext{mL} 	imes 0.789\ 	ext{g/mL} 	imes \frac{1\ 	ext{mol}}{46.0688\ 	ext{g}}}{0.2500\ 	ext{L}} = 1.71\ 	ext{M}$$

Question 8

Which of the following best explains why most reactions in general chemistry are conducted in solution?

Accepted Answer

Solutions allow atoms, ions, or molecules to collide faster and easier, increasing reaction rates.

Question 9

A stock solution of HCl has a concentration of 12.8 M. What volume of this stock solution is required to prepare 250.0 mL of 0.1000 M HCl?

Accepted Answer

$$V_1$$ = \frac{0.1000\ 	ext{M} 	imes 250.0\ 	ext{mL}}{12.8\ 	ext{M}} = 1.95\ 	ext{mL}$$

Question 10

Which laboratory glassware would provide the most accurate measurement for preparing exactly 100.0 mL of a solution?

Accepted Answer

A 100.0 mL volumetric flask

Question 11

A solution is labeled as NaCl(aq). What does this notation indicate?

Accepted Answer

Sodium chloride is dissolved in water, but the relative amounts are not specified.

Question 12

If 200.0 mL of water is added to 100.0 mL of 0.150 M NaCl, what is the resulting concentration, assuming volumes are additive?

Accepted Answer

$$M_2$$ = \frac{0.150\ 	ext{M} 	imes 100.0\ 	ext{mL}}{300.0\ 	ext{mL}} = 0.0500\ 	ext{M}$$

Question 13

Which of the following statements about dilution is correct?

Accepted Answer

All the solute from the original concentrated solution is found in the final diluted solution.

Question 14

Which of the following is the correct formula for calculating molality ($$m$$)?

Accepted Answer

$$m = \frac{	ext{mol solute}}{	ext{kg solvent}}$$

Question 15

A glass cleaner contains isopropanol, ammonia, a wetting agent, and a colorant. What does this illustrate about solutions?

Accepted Answer

Solutions may contain more than one solute.

Question 16

Which of the following is a reason why volumetric flasks are preferred for preparing standard solutions?

Accepted Answer

They have a single calibration line for precise volume measurement.

Molarity, Solution Preparation, and Dilution in General Chemistry

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