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Topic 6: Mole and stoichiometry - Mathematics of formulas and equations

8. Molecular formulas: Determining molecular formula from molecular mass and empirical formula

1. What is the molecular formula of a compound with a molecular mass of 56 g and an empirical
formula of CH2?
1) CH2 2) C2H4 3) C3H6 4) C4H8

x 100

x 100
x 100
x 100

2. What is the molecular formula of a compound with a molecular mass of 78 g/mol and an empirical
formula of CH?
1) C3H3 2) C4H4 3) C6H6 4) C4H10

3. A compound has a molecular mass of 284 g and an empirical formula of P2O5. What is the molecular
formula of this compound?
1) P4O10 2) P5O2 3) P2O5 4) P10O4

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4. A compound has an empirical formula of HCO2 and a mass of 90 g/mole. What is the molecular
formula of this compound? 2) H2C2O4 3) H4C4O8 4) H6C6O12

1) HCO

5. A compound has an empirical formula of CH2Br and a molecular mass of 188 grams per mole. What is
the molecular formula of this compound?
1) CH2Br 2) C2H4Br2 3) C3H6Br3 4) CHBr2

9. Ratio of composition: Determining ratio by mass of atoms in a formula

1. What is the ratio by mass of sulfur to oxygen in the formula SO4?
1) 1 : 1 2) 1 : 2 3) 2 : 1 4) 1 : 4

2. What is the ratio by mass of carbon to hydrogen in the CH4?

1) 1 : 4
2) 3 : 1

3) 3 : 1

this formula? Teacher Preview Copy 4) 1 : 6

3. What is the approximate ratio by mass of carbon to hydrogen in the formula C5H10?
1 ) 1 : 2 2) 6 : 1 3) 1 : 6 4) 1 : 5

4. What is the approximate ratio by mass of hydrogen to oxygen in the formula H2O?
1) 2 : 1 2) 2 : 1 3) 1 : 8 4) 1 : 8

5. What is the approximate ratio by mass of Lithium to chloride in the gram formula mass of LiCl?
1) 3 : 17 2) 1 : 5 3) 1 : 1 4) 1 : 2

6. The ratio by mass of carbon to hydrogen to oxygen in 1 mole of C6H12O6 is
1) 6 : 1 : 8 2) 3 : 1 : 4 3) 1 : 2 : 1 4) 2 : 6: 2

7. Acetic acid has a formula of HC2H3O2. What is the ratio by mass of hydrogen to carbon to oxygen in
1) 1 : 2 : 2 2) 2 : 3 : 3 3) 1 : 6 : 8 4) 1 : 2 : 4

8. What is the ratio by mass of hydrogen to carbon to oxygen in the formula CH3OH?
1) 4 : 1 : 1 2) 1 : 3 : 1 3) 4: 3: 2 4) 1 : 3 : 4

9. In magnesium oxide formula, what is the ratio by mass of magnesium to oxygen ?
1) 3: 2 2) 1 : 1 3) 2 : 1 4) 3 : 4

10. When the formula for calcium bromide is correctly written, the ratio by mass of calcium to bromine is

1) 1 : 2 2) 1: 1 3) 4 : 1 4) 1 : 4

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