10th grade Percent composition of a compound worksheet

Percent composition of a compound

Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Water is 88.8% oxygen by mass. How many grams of oxygen are in 50 g of water, to 0.01 g, Bo?
2. 2.

   Baking soda is 27.4% sodium by mass. How many grams of sodium are in 200 g of baking soda, to 0.01 g, Esme?
3. 3.

   Glucose is 40% carbon by mass. How many grams of carbon are in 250 g of glucose, to 0.01 g, Jun?
4. 4.

   Which element makes up the most of baking soda's mass (NaHCO₃), Luz?

   • Hydrogen, since each element counts the same
   • Oxygen, at 57.1%
   • Sodium, since it is named first
5. 5.

   Which makes up more of sugar's mass (C₁₂H₂₂O₁₁): its 22 H atoms or its 12 C atoms, Milo?

   • The hydrogen, since there are more H atoms
   • The carbon: 42.1% against 6.5%
   • They match, since each atom weighs the same
6. 6.

   Which is a higher percent oxygen by mass: water or carbon dioxide, Pia?

   • Carbon dioxide, since it has two O atoms
   • Water, at 88.8% against 72.7% for CO₂
   • Neither; oxygen is 50% of each
7. 7.

   Salt is 39.3% sodium and baking soda is 27.4% sodium. Which gives more sodium in 10 g, Ren?

   • Baking soda, since its formula is longer
   • Salt: 3.93 g against 2.74 g
   • They match, since both samples are 10 g
8. 8.

   A 20 g and a 2,000 g sample of pure salt: what percent sodium is each, Tala?

   • 39.3% for both, since both are NaCl
   • The bigger sample is a higher percent sodium
   • The smaller sample is a higher percent sodium
9. 9.

   Why is a sample of pure water 11.2% hydrogen by mass at any size, Zee?

   • Water is weighed at 11.2 g each time
   • Bigger samples hold extra hydrogen
   • Each molecule has the same 2 H and 1 O
10. 10.

    A lab finds 4.48 g of hydrogen in 40.0 g of water. Does this match water's 11.2%, Ari?

    • No: 40.0 ÷ 4.48 × 100 is far above 11.2%
    • No: a bigger sample should give a bigger percent
    • Yes: 4.48 ÷ 40.0 × 100 = 11.2%