Q: A solution is prepared by dissolving 15.8 g of glucose ($C_6H_{12}O_6$) in 200.0 g of water. What is the mass percent of glucose in the solution?

$\frac{15.8}{215.8} \times 100 = 7.32\%$

Q: Which of the following is the correct formula for calculating mass/volume percent ($\%$ m/v) of a solution?

$\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}} \times 100$

Q: A sample of bleach contains 2.7 g of sodium hypochlorite ($NaOCl$) in 500.0 mL of solution. What is the mass/volume percent of $NaOCl$ in the bleach?

$\frac{2.7}{500.0} \times 100 = 0.54\%$

Q: A solution contains 0.012 g of Ni in 85.0 g of body tissue. What is the concentration of Ni in parts per million (ppm)?

$\frac{0.012}{85.0} \times 10^6 = 141$ ppm

Q: Which of the following is the correct formula for converting mass percent to grams of solute in a given mass of solution?

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

Question 1

A hospital IV bag contains 0.9% NaCl solution by mass. If the bag contains 500 g of solution, how many grams of NaCl are present in the bag?

Accepted Answer

$0.009 	imes 500 = 4.5$ g

Question 2

Which of the following best describes the term 'solubility' as used in chemistry?

Accepted Answer

The maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature

Question 3

A solution is prepared by dissolving 15.8 g of glucose ($C_6H_{12}O_6$) in 200.0 g of water. What is the mass percent of glucose in the solution?

Accepted Answer

$\frac{15.8}{215.8} 	imes 100 = 7.32\%$

Question 4

Which of the following is the correct formula for calculating mass/volume percent ($\%$ m/v) of a solution?

Accepted Answer

$\frac{	ext{mass of solute (g)}}{	ext{volume of solution (mL)}} 	imes 100$

Question 5

A sample of bleach contains 2.7 g of sodium hypochlorite ($NaOCl$) in 500.0 mL of solution. What is the mass/volume percent of $NaOCl$ in the bleach?

Accepted Answer

$\frac{2.7}{500.0} 	imes 100 = 0.54\%$

Question 6

Which of the following statements about saturated and unsaturated solutions is correct?

Accepted Answer

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

Question 7

A solution contains 0.012 g of Ni in 85.0 g of body tissue. What is the concentration of Ni in parts per million (ppm)?

Accepted Answer

$\frac{0.012}{85.0} 	imes 10^6 = 141$ ppm

Question 8

Which of the following is the correct definition of molarity ($M$)?

Accepted Answer

Moles of solute per liter of solution

Question 9

What is the molarity of a solution prepared by dissolving 2.50 g of $NaOH$ in enough water to make 750 mL of solution? ($NaOH$ molar mass = 40.00 g/mol)

Accepted Answer

$\frac{2.50}{40.00} = 0.0625$ mol; $\frac{0.0625}{0.750} = 0.0833$ M

Question 10

A coffee cup contains 0.150 g of caffeine ($C_8H_{10}N_4O_2$) in 350.0 mL of coffee. What is the molarity of caffeine in the coffee? (Molar mass = 194.19 g/mol)

Accepted Answer

$\frac{0.150}{194.19} = 0.000772$ mol; $\frac{0.000772}{0.350} = 0.00221$ M

Question 11

Which of the following is the correct formula for converting mass percent to grams of solute in a given mass of solution?

Accepted Answer

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

Question 12

A solution is labeled as 5% v/v ethanol in water. What does this mean?

Accepted Answer

5 mL of ethanol is present in every 100 mL of solution

Question 13

A sample contains 21 ppm of cobalt in water. How many grams of cobalt are present in 1.00 L of solution?

Accepted Answer

$21 	ext{ mg} = 0.021 	ext{ g}$

Question 14

Which of the following is NOT a correct use of percent concentration in chemical calculations?

Accepted Answer

To calculate the molarity of a solution directly from percent concentration without additional information

Question 15

A solution is prepared by dissolving 10.0 g of $KBr$ in enough water to make 250.0 mL of solution. What is the molarity of the solution? ($KBr$ molar mass = 119.0 g/mol)

Accepted Answer

$\frac{10.0}{119.0} = 0.0840$ mol; $\frac{0.0840}{0.250} = 0.336$ M

Question 16

Which of the following best explains why knowing the solubility of a solute does not always accurately represent the amount of solute dissolved in a solution?

Accepted Answer

Solubility is a theoretical value and does not account for temperature changes or impurities.

Question 17

A 12.77% (w/v) solution of glucose ($C_6H_{12}O_6$) in water is needed to obtain 50.0 g of $C_6H_{12}O_6$. What volume of solution is required?

Accepted Answer

$\frac{50.0}{12.77} 	imes 100 = 392$ mL

Question 18

Which of the following is the correct formula for calculating weight/weight percent ($\%$ w/w) of a solution?

Accepted Answer

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

Solutions and Concentration: Solubility, Percent Composition, and Molarity

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