If a solution has 58.5% NaCl by mass and you have 200.0 g of this solution, how many grams of NaCl are present?

If a solution has 58.5% NaCl by mass and you have 200.0 g of this solution, how many grams of NaCl are present?

• A. 117.0 g
• B. 58.5 g
• C. 100.0 g
• D. 50.0 g

Answer: (A)

Mass percent tells you what portion of the total mass is the solute. A solution that is 58.5% NaCl by mass has 58.5 g of NaCl in every 100 g of solution. To find the amount in 200.0 g of solution, multiply by the fraction: (58.5/100) × 200.0 g = 117.0 g. In other words, doubling the 100 g case doubles the NaCl mass, giving 117.0 g. The other numbers would apply to different total masses or different percentages, not this 200.0 g sample with 58.5% NaCl.

Mass percent tells you what portion of the total mass is the solute. A solution that is 58.5% NaCl by mass has 58.5 g of NaCl in every 100 g of solution. To find the amount in 200.0 g of solution, multiply by the fraction: (58.5/100) × 200.0 g = 117.0 g. In other words, doubling the 100 g case doubles the NaCl mass, giving 117.0 g. The other numbers would apply to different total masses or different percentages, not this 200.0 g sample with 58.5% NaCl.