Percent by Mass and Percent by Volume

Percent Solutions (mass and volume)

By Susan Duderstadt

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Sometimes concentration is expressed as a percent

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Ratio of mass of solute to mass of solution

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Percent by mass

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Multiple Choice

Think Carefully: When we are calculating percent by mass for solutions, what is our denominator?

• The mass of the solute

• The mass of the solvent

• The molar mass of the solute

• The mass of the solute PLUS the mass of the solvent

Example

You are making a solution with 25g of sucrose and 100 g of water.​

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What is your percent by mass? ​

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Multiple Choice

You are making a solution with 25g of sucrose and 100 g of water.​

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What is your percent by mass? ​

• 25%

• 20%

• 100%

• 15%

The total volume of our solution is :

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25 g of sucrose + 100 g of water

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= 125 g of solution

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Multiple Choice

What is the concentration, in percent by mass, of 0.62 g of solute in 45.0 g of solution?

• 0.014 %

• 1.4 %

• 0.13%

Multiple Choice

What is the percent by mass of a solution made by dissolving 10.0 g of NaCl into 180.0 g of water?

• 5.26 %

• 5.56 %

• 180.0 %

• 20.0 %

Multiple Choice

What mass of solute is needed to make 100.0 g of a 3.4% solution?

• 3.4 g

• 34 g

• 2941 g

• 0.34 g

Ratio of the volume of solute to the volume of solution​

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Percent by volume

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​Example

if we add 40 mL of ethanol to 200 mL of water, what is the percent by volume?

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Multiple Choice

What is the concentration, in percent by volume, of 15.3 mL of solute in 2.65 L of solution?

Hint: Pay attention to your units!

• 0.58%
• 0.0058%
• 5.8%