# Worksheet: Percentage Composition

In this worksheet, we will practice calculating the percentage composition of a material using chemical formulas or the masses of constituent elements.

**Q1: **

A 5.0 g sample of spinal fluid contains 3.75 mg (0.00375 g) of glucose. What is the percent by mass of glucose in spinal fluid?

**Q2: **

A bottle of a tile cleanser contains 135 g of and 775 g of water. What is the percent by mass of in this cleanser?

**Q3: **

A compound contains only the elements and . A sample of the compound with a mass of 12.5 g is found to contain 6.50 g of . What is the percentage composition of the compound?

- A 48.0%, 52.0%
- B 50.0%, 50.0%
- C 44.5%, 55.5%
- D 52.0%, 48.0%
- E 55.5%, 44.5%

**Q4: **

A 10 g sample of silicon carbide is found to contain 3.0 g of carbon. What is the percentage composition of silicon carbide?

- A 50%, 50%
- B 70%, 30%
- C 25%, 75%
- D 30%, 70%
- E 75%, 25%

**Q5: **

What is the percentage composition of calcium carbonate ? State percentages to 1 decimal place.

- A 20.0%, 20.0%, 60.0%
- B 33.3%, 33.3%, 33.3%
- C 58.9%, 17.6%, 23.5%
- D 40.0%, 12.0%, 48.0%
- E 20.0%, 60.0%, 20.0%

**Q6: **

To 1 decimal place, calculate the oxygen content of a water molecule as a percentage of the total mass.