Q: If you have a solution containing 12.0 g of urea $$(\mathrm{NH_2CONH_2})$$ and 100.0 g of water, what is the mass percent of urea in the solution?

$$\frac{12.0}{112.0} \times 100\% = 10.7\%$$

Q: A chemist needs to prepare 250 g of a $$5.0\%$$ NaCl solution. How many grams of NaCl are required?

$$\frac{5.0}{100} \times 250 = 12.5$$ grams

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

$$\text{Mass Percent} = \frac{\text{Mass Component}}{\text{Total Mass}} \times 100\%$$

Q: A solution is made by dissolving 11.0 g of KBr in 210 g of water. What is the mass percent of KBr in the solution?

$$\frac{11.0}{221.0} \times 100\% = 4.98\%$$

Q: A laboratory technician needs to dilute a $$40.0\%$$ sugar solution to make $$200$$ grams of a $$10.0\%$$ sugar solution. How many grams of the original solution should be used?

$$\frac{10.0}{40.0} \times 200 = 50$$ grams

Q: A solution is made by mixing $$15.0$$ grams of ethanol with $$85.0$$ grams of water. What is the mass percent of ethanol in the solution?

$$\frac{15.0}{100.0} \times 100\% = 15.0\%$$

Q: A chemist wants to prepare $$500$$ grams of a $$2.0\%$$ KCl solution. How many grams of KCl are needed?

$$\frac{2.0}{100} \times 500 = 10$$ grams

Question 1

Which of the following best defines mass percent in the context of a solution?

Accepted Answer

The ratio of the mass of solute to the total mass of solution, multiplied by 100%.

Question 2

A solution is prepared by dissolving 23.0 grams of NaOH in enough water to make 100 grams of solution. What is the mass percent of NaOH in the solution?

Accepted Answer

$$23.0\%$$

Question 3

If you have a solution containing 12.0 g of urea $$(\mathrm{NH_2CONH_2})$$ and 100.0 g of water, what is the mass percent of urea in the solution?

Accepted Answer

$$\frac{12.0}{112.0} 	imes 100\% = 10.7\%$$

Question 4

A chemist needs to prepare 250 g of a $$5.0\%$$ NaCl solution. How many grams of NaCl are required?

Accepted Answer

$$\frac{5.0}{100} 	imes 250 = 12.5$$ grams

Question 5

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

Accepted Answer

$$	ext{Mass Percent} = \frac{	ext{Mass Component}}{	ext{Total Mass}} 	imes 100\%$$

Question 6

A solution is made by dissolving 11.0 g of KBr in 210 g of water. What is the mass percent of KBr in the solution?

Accepted Answer

$$\frac{11.0}{221.0} 	imes 100\% = 4.98\%$$

Question 7

If a solution contains $$x$$ grams of solute and $$y$$ grams of solvent, which equation gives the total mass of the solution?

Accepted Answer

$$x + y$$

Question 8

A saline solution contains $$9.0$$ grams of NaCl in $$100.0$$ grams of solution. What is the mass percent of NaCl?

Accepted Answer

$$9.0\%$$

Question 9

A laboratory technician needs to dilute a $$40.0\%$$ sugar solution to make $$200$$ grams of a $$10.0\%$$ sugar solution. How many grams of the original solution should be used?

Accepted Answer

$$\frac{10.0}{40.0} 	imes 200 = 50$$ grams

Question 10

Which of the following statements about mass percent is FALSE?

Accepted Answer

Mass percent can never exceed $$100\%$$ for a solution.

Question 11

A solution is made by mixing $$15.0$$ grams of ethanol with $$85.0$$ grams of water. What is the mass percent of ethanol in the solution?

Accepted Answer

$$\frac{15.0}{100.0} 	imes 100\% = 15.0\%$$

Question 12

A chemist wants to prepare $$500$$ grams of a $$2.0\%$$ KCl solution. How many grams of KCl are needed?

Accepted Answer

$$\frac{2.0}{100} 	imes 500 = 10$$ grams

Solutions: Mass Percent in Chemistry

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