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 H C l and 775 g of water. What is the percent by mass of H C l in this cleanser?

Q3:

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

  • A X : 48.0%, Y : 52.0%
  • B X : 50.0%, Y : 50.0%
  • C X : 44.5%, Y : 55.5%
  • D X : 52.0%, Y : 48.0%
  • E X : 55.5%, Y : 44.5%

Q4:

A 10 g sample of silicon carbide ( S i C ) is found to contain 3.0 g of carbon. What is the percentage composition of silicon carbide?

  • A C : 50%, S i : 50%
  • B C : 70%, S i : 30%
  • C C : 25%, S i : 75%
  • D C : 30%, S i : 70%
  • E C : 75%, S i : 25%

Q5:

What is the percentage composition of calcium carbonate ( C a C O ) 3 ? State percentages to 1 decimal place.

  • A C a : 20.0%, C : 20.0%, O : 60.0%
  • B C a : 33.3%, C : 33.3%, O : 33.3%
  • C C a : 58.9%, C : 17.6%, O : 23.5%
  • D C a : 40.0%, C : 12.0%, O : 48.0%
  • E C a : 20.0%, C : 60.0%, O : 20.0%

Q6:

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

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