Percent composition of a compound
Grade 10 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A lab analysis of 10 g of table sugar finds 4.21 g of carbon. What percent carbon is that, to 0.1%, Esme?
A lab analysis of 9 g of water finds 1.01 g of hydrogen. What percent hydrogen is that, to 0.1%, Jun?
Bo says water is 66.7% hydrogen because 2 of its 3 atoms are hydrogen. Which reply fits, Luz?
- Agree, for small samples of water
- Agree: percent composition counts atoms, not their masses
- Disagree: by mass, hydrogen is just 11.2%
Ren says a 2 kg bag of baking soda is a higher percent sodium than a 1 g pinch. Which reply fits, Milo?
- Agree: a bigger sample holds a bigger share of sodium
- Agree: the pinch has lost some sodium to the air
- Disagree: both are 27.4% sodium
Zee says the element percents in a compound add to 100%. Which reply fits, Noah?
- Disagree: each element is 100% of itself, so they add to 300%
- Agree: glucose's 40.0% + 6.7% + 53.3% = 100%
- Disagree: they add to the molar mass, 180.18
Glucose has 6 C atoms at 12.01 g/mol in 180.18 g/mol. What percent of its mass is carbon, Pia?
- 6.7%
- 25.0%
- 40.0%
Glucose has 6 O atoms at 16.00 g/mol in 180.18 g/mol. What percent of its mass is oxygen, Tala?
- 25.0%
- 8.9%
- 53.3%
Two labs test pure water from two cities. What percent hydrogen should both find, Zee?
- 11.2%, since pure water is always H₂O
- Different values, since each city's water is different
- 66.7%, since 2 of 3 atoms are H
A sample sold as pure salt tests at 45.0% sodium. What does that suggest, Ari?
- It is not pure salt, which is 39.3% sodium
- It is pure salt from a larger sample
- It is pure salt, since salt's percent can vary
Which percent bar fits carbon dioxide (CO₂), Bo?
- C 50.0%, O 50.0%
- C 27.3%, O 72.7%
- C 33.3%, O 66.7%