Percent Composition

Baking soda, used in cooking and cleaning, is made of the elements sodium, hydrogen, carbon, and oxygen. If baking soda is 27.3 % Na, 1.2 % H, and 14.3 % carbon, what is the mass percentage of oxygen?

• 57.2 %

• 42.8 %

• 85.6 %

• 26.9 %

Rust is a compound of iron and oxygen. If in a 48.0 g piece of rust, there are 14.4 g of oxygen. What is the mass of iron in the sample?

• 33.6 g iron

• 62.4 g iron

• 3.33 g iron

• 0.300 g iron

Tags

NGSS.HS-PS1-7

Ammonia, found in cleaning products, is a compound of nitrogen and hydrogen. If ammonia is 82.2 % nitrogen, what is the percentage of hydrogen?

• 17.8 % hydrogen

• 82.2 % hydrogen

• 64.4 % hydrogen

• 8.9 % hydrogen

In 75.0 g of quicklime (used in making cement) there are 53.6 g of calcium and 21.4 g of oxygen. What is the mass percent of calcium in this compound?

• 71.5 % calcium

• 28.5 % calcium

• 21.4 % calcium

• 88.3 % calcium

Natural gas is a compound made of carbon and hydrogen. In 5.00 g of natural gas it is found there are 1.26 g of hydrogen and 3.74 g of carbon. What is the mass percent of hydrogen in natural gas?

• 25.2 % hydrogen

• 74.8 % hydrogen

• 33.7 % hydrogen

• 68.2 % hydrogen

Tags

NGSS.HS-PS1-3

Carbon monoxide, a poisonous gas produced when furnaces and stove malfunction, is a compound of carbon and oxygen. If in 25.0 g of carbon monoxide there are 10.7 g of carbon, what mass of oxygen is present?

• 14.3 g oxygen

• 35.7 g oxygen

• 2.34 g oxygen

• 0.428 g oxygen

Tags

NGSS.HS-PS1-7

Xenon hexafluoride is 53.5 % xenon, by mass. If a 10.0 g sample of an unknown gas contains 3.45 g of xenon, could this be xenon hexafluoride?

• Yes, the mass percent is the same.

• No, the mass percent is different.

• Yes, the mass percent is different.

• No, the mass percent is the same.

Tags

NGSS.HS-PS1-7

In 2.30 g of table salt, sodium chloride, there are 0.90 g of sodium and 1.40 g of chlorine. What is the mass percent of sodium in sodium chloride?

• 39.1 % sodium

• 60.9 % sodium

• 65.3 % sodium

• 155 % sodium

Tags

NGSS.HS-PS1-7

A 10.0 g piece of stainless steel is found to contain 10.1% manganese by mass. What is the mass percent of manganese in a 100.0 g piece of the same metal?

• 10.1 %

• 100.1 %

• 1.01 %

• 0.101 %

Answer explanation

The mass percent is always the same, regardless of the sample size.

Sodium acetate is 28.0 % sodium, 29.3 % carbon, 3.7 % hydrogen and 39.0 % oxygen. If an unknown solid is found to contain 7.33 g of carbon per 25.0 g of sample, could this be sodium acetate?

• Yes

• No

Answer explanation

Yes, the mass percent of carbon is 29.3 %, consistent with sodium acetate.

Tags

NGSS.HS-PS1-7