# Worksheet: Moles

In this worksheet, we will practice defining the mole in terms of Avogadro’s constant and converting the mass of a substance to an amount of moles.

**Q2: **

Sulfuric acid has a relative formula mass of 98 g/mol. What is the mass of 2.5 mol of sulfuric acid, to 3 significant figures?

**Q3: **

Ammonia has a relative formula mass of 17. How many moles of ammonia molecules are there in 34 g of ammonia?

**Q4: **

A 24 g sample of lithium hydride contains 3.0 moles of units. What is the relative formula mass of lithium hydride?

**Q5: **

The mass of a substance , its relative formula mass , and the number of moles present can be related by a single formula. What is that formula?

- A
- B
- C
- D
- E

**Q6: **

How many moles of atoms are there in 12 g of carbon-12?

**Q7: **

How is the atomic mass unit (u) defined?

- A1 u is equal to the mass of a neutron.
- B1 u is equal to th of the mass of a carbon-12 atom.
- C1 u is equal to the mass of a proton.
- D1 u is equal to the mass of a carbon-12 atom.
- E1 u is equal to the mass of a hydrogen-1 atom.

**Q9: **

To 3 significant figures, how many atomic mass units (u) are there in one gram (g) of a substance?

- A
- B
- C
- D
- E

**Q14: **

The standard unit for measuring the amount of a substance is the mole.

How many entities does one mole of a substance contain? Give your answer to 4 significant figures.

- A
- B
- C
- D
- E

What is this numerical value called?

- AFaraday’s constant
- BAvogadro’s constant
- CPlanck’s constant
- DTaylor’s constant
- EBoltzmann’s constant

**Q15: **

The recommended daily intake of selenium for an adult is approximately 0.068 mg. How many moles of selenium is this?

- A
- B
- C
- D
- E

**Q16: **

As a molar percentage, 80.3% of a boron sample is and the remainder is . What is the average molar mass of the boron sample?