Question

Exercises (Mass Percent) 1. 3.0 grams of sugar are dissolved in 150 g of water What is the mass percent of sugar in the solution? 2. A 200-gram solution of alcohol contains 180 mL of water. What is the mass percent of alcohol? (Remember water's density.) 3. How many grams of NaBr are needed to make 50 g of a 5.0% solution? 4. How many grams of LiOH are needed to make 25 g of a 4.0% solution? 5. What mass of NaF must be mixed with 25 mL of water to create a 3.5% by mass solution? 6. An 800 g solution of Kool-Aid contains 780 g of water. What is the mass percent of solute in this solution? 7. What is the mass percent of a solution created by adding 10 g of olive oil to 90 g of vegetable oil? 8. If a 4000g solution of salt water contains 40g of salt, what is its mass percent?

Answer 1

1)
mass % of sugar = mass of sugar * 100 / mass of solution
= 5.0 * 100 / (5.0 + 150)
= 3.23 %
Answer: 3.23 %

2)
mass of alcohol = mass of solution - mass of water
= 200 g - 180 g
= 20 g

mass % of alcohol = mass of alocohol * 100 / mass of solution
= 20 * 100 / 200
= 10.0 %
Answer: 10.0 %

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