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Worksheet: Percentage Composition from Molecular Formulas

Q1:

What is the empirical formula of a compound containing 4 0 . 0 0 % C , 6 . 7 1 % H , and 5 3 . 2 8 % O ?

  • A C H O 2 2 2
  • B C H O 4
  • C C H O 3 2
  • D C H O 2
  • E C H O 2 4

Q2:

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

  • AHalite, N a C l
  • BLimestone, C a C O 3
  • CBeryl, B e A l S i O 3 2 6 1 8
  • DTurquoise, C u A l ( P O ) ( O H ) ( H O ) 6 4 4 8 2 4
  • EMalachite, C u ( O H ) C O 2 2 3

Q3:

What is the mass percentage of ammonia in C o ( N H ) C l 3 6 3 ?

Q4:

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

  • A C H C l 3
  • B C H 4
  • C C H C H F 2
  • D C H C H 3 3
  • E C H C H B r 2

Q5:

A compound of carbon and hydrogen contains 8 5 . 6 % C and has a molar mass of 28.1 g/mol. What is its molecular formula?

  • A C H 2 2
  • B C H 4
  • C C H 2 6
  • D C H 2 4
  • E C H 3 6

Q6:

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 silver(I) bromide. As a percentage of the total mass, calculate the quantity of gallium present in the sample of gallium(III) bromide.

Q7:

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

  • A C H O 1 2 1 0 6
  • B C H C l 3
  • C C H C H C H C H C H 3 2 2 2 3
  • D C H 4
  • E C H 2 4

Q8:

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

What is the empirical formula?

  • A C H
  • B C H 3
  • C C H 4
  • D C H 2
  • E C H 2

If 1.56 g of the hydrocarbon occupies a volume of 1.00 L at 0.984 atm and 5 0 C what is the molecular formula?

  • A C H 3 6
  • B C H 2 2
  • C C H 6 1 0
  • D C H 3 8
  • E C H 5 1 0

Q9:

What is the empirical formula for a substance which is 3 2 . 0 % oxygen and 6 8 . 0 % vanadium, by mass?

  • A V O 2
  • B V O
  • C V O 2 5
  • D V O 2 3

Q10:

What is the empirical formula for a substance which is 4 3 . 7 % oxygen and 5 6 . 3 % phosphorus, by mass?

  • A P O 3
  • B P O 2 5
  • C P O 5
  • D P O 2 3
  • E P O 4

Q11:

Analysis of a 12.04-g sample of a liquid compound composed of carbon, hydrogen, and nitrogen showed it to contain 7 . 3 4 g C , 1 . 8 5 g H , and 2 . 8 5 g N . What is the percent composition of this compound?

  • A 1 5 . 4 % C , 2 3 . 7 % H , 6 1 . 0 % N
  • B 6 0 . 1 % C , 1 4 . 3 % H , 2 5 . 6 % N
  • C 5 5 . 7 % C , 1 6 . 0 % H , 2 8 . 4 % N
  • D 6 1 . 0 % C , 1 5 . 4 % H , 2 3 . 7 % N
  • E 4 0 . 9 % C , 1 3 . 2 % H , 4 5 . 9 % N

Q12:

A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 7 5 . 9 5 % C , 1 7 . 7 2 % N , and 6 . 3 3 % H by mass with a molar mass of about 240 g/mol.

What is the empirical formula of the dye?

  • A C H N 5 4 2
  • B C H N 4 6
  • C C H N 4 5 2
  • D C H N 5 5
  • E C H N 3 3

What is the molecular formula of the dye?

  • A C H N 1 5 1 5 3
  • B C H N 1 2 1 5 6
  • C C H N 1 5 1 2 6
  • D C H N 1 2 1 8 3
  • E C H N 9 9 3

Q13:

A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 7 5 . 9 5 % C , 1 7 . 7 2 % N , and 6 . 3 3 % H by mass with a molar mass of about 240 g/mol.

What is the empirical formula of the dye?

  • A C H N 5 4 2
  • B C H N 4 6
  • C C H N 4 5 2
  • D C H N 5 5
  • E C H N 3 3

What is the molecular formula of the dye?

  • A C H N 1 5 1 5 3
  • B C H N 1 2 1 5 6
  • C C H N 1 5 1 2 6
  • D C H N 1 2 1 8 3
  • E C H N 9 9 3

Q14:

What is the empirical formula for a substance which is 4 6 . 6 % oxygen and 5 3 . 4 % manganese, by mass?

  • A M n O 3 4
  • B M n O
  • C M n O 2 3
  • D M n O 3
  • E M n O 2

Q15:

In the metal complex C o ( N H ) C l 3 6 3 , which element makes up the largest proportion by mass?

  • ANitrogen
  • BHydrogen
  • CCobalt
  • DChlorine