# Worksheet: Percentage Composition from Molecular Formulas

In this worksheet, we will practice converting between elemental percentage compositions, empirical formulas, and molecular formulas.

Q1:

Adding aqueous silver(I) nitrate to aqueous gallium(III) bromide results in the precipitation of silver(I) bromide. A sample of gallium(III) bromide weighing 0.165 g was dissolved in water and treated with silver(I) nitrate, resulting in the precipitation of 0.299 g of silver(I) bromide. Calculate the quantity of the reacted gallium present in the sample of gallium(III) bromide, as a percentage of the total mass.

Q2:

What is the empirical formula of a compound containing , , and ?

• A
• B
• C
• D
• E

Q3:

What is the empirical formula for a substance that is oxygen and manganese by mass?

• A
• B
• C
• D
• E

Q4:

What is the empirical formula for a substance that is oxygen and vanadium by mass?

• A
• B
• C
• D

Q5:

Which of the following compounds has the highest percentage mass of carbon?

• A
• B
• C
• D
• E

Q6:

A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 75.95% , 17.72% , and 6.33% by mass with a molar mass of about 240 g/mol.

What is the empirical formula of the dye?

• A
• B
• C
• D
• E

What is the molecular formula of the dye?

• A
• B
• C
• D
• E

Q7:

A hydrocarbon is composed of 85.7% carbon and 14.3% hydrogen by mass.

What is the empirical formula?

• A
• B
• C
• D
• E

If 1.56 g of the hydrocarbon occupies a volume of 1.00 L at 0.984 atm and , what is the molecular formula?

• A
• B
• C
• D
• E

Q8:

What is the empirical formula for a substance that is oxygen and phosphorus by mass?

• A
• B
• C
• D
• E

Q9:

A compound of carbon and hydrogen contains and has a molar mass of 28.1 g/mol. What is its molecular formula?

• A
• B
• C
• D
• E

Q10:

A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of , , and by mass with a molar mass of about 240 g/mol.

What is the empirical formula of the dye?

• A
• B
• C
• D
• E

What is the molecular formula of the dye?

• A
• B
• C
• D
• E

Q11:

Which of these molecules has the highest percentage mass of hydrogen?

• A
• B
• C
• D
• E

Q12:

Which of these minerals has the highest mass percentage of oxygen?

• ATurquoise,
• BMalachite,
• CLimestone,
• DBeryl,
• EHalite,

Q13:

What is the mass percentage of ammonia in ?

Q14:

In the metal complex , which element makes up the largest proportion by mass?

• AChlorine
• BNitrogen
• CHydrogen
• DCobalt

Q15:

Analysis of a 12.04 g sample of a liquid compound composed of carbon, hydrogen, and nitrogen showed it to contain , , and . What is the percent composition of this compound?

• A, ,
• B, ,
• C, ,
• D, ,
• E, ,

Q16:

Nicotine, an alkaloid in the nightshade family of plants that is mainly responsible for the addictive nature of cigarettes, contains 74.02% , 8.710% , and 17.27% . If 40.57 g of nicotine contains 0.2500 mol nicotine, what is the molecular formula?

• A
• B
• C
• D
• E

Q17:

The bacterial fermentation of grain to produce ethanol forms a gas with a percent composition of 27.29% and 72.71% . What is the empirical formula for this gas?

• A
• B
• C
• D
• E