Percent Composition by Mass

What is the gram-formula mass of Mg(NO₃)₂?

• 86 g/mol

• 134 g/mol

• 148 g/mol

• 172 g/mol

What is the percent composition by mass of nitrogen in the compound N₂H₄ (gram-formula mass = 32 g/mol)?

• 13%

• 44%

• 88%

• 93%

Which compound has the greatest percent composition by mass of sulfur?

• BaS

• CaS

• MgS

• SrS

Which compound has the highest percent composition by mass of strontium?

• SrCl₂

• SrI₂

• SrO

• SrS

Which compound has the smallest percent composition by mass of chlorine?

• HCl

• KCl

• LiCl

• NaCl

Base your answer to the question on the information below.

Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person’s diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C₆H₈O₆ and a gram-formula mass of 176 grams per mole.

Which is a correct setup for calculating the percent composition by mass of oxygen in ascorbic acid?

What is the formula mass of (NH₄)₃PO₄?

• 113

• 121

• 149

• 404

Which contains the greatest percent by mass of hydrogen?

• OH^-

• H₂O

• H₃O⁺

• H₂O₂

Tags

NGSS.MS-PS1-1

Arsenic is often obtained by heating the ore arsenopyrite, FeAsS. The decomposition of FeAsS is represented by the balanced equation below.

In the solid phase, arsenic occurs in two forms. One form, yellow arsenic, has a density of 1.97 g/cm³ at STP. The other form, gray arsenic, has a density of 5.78 g/cm³ at STP. When arsenic is heated rapidly in air, arsenic(III) oxide is formed.

Although arsenic is toxic, it is needed by the human body in very small amounts. The body of a healthy human adult contains approximately 5 milligrams of arsenic.

Calculate the percent composition by mass of arsenic in arsenopyrite.

Tags

NGSS.HS-PS1-2

What is the percent composition by mass of hydrogen in NH₄HCO₃ (gram-formula mass = 79 grams/mole)?

• 5.1%

• 6.3%

• 10.1%

• 50.5%