# 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.

Q1:

What is the mass of 0.443 mol of hydrazine, ?

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.

Q8:

A prospector panning for gold in a river collects 15.81 g of pure gold. Calculate, to 3 significant figures, the number of atoms in this quantity of gold.

• A atoms
• B atoms
• C atoms
• D atoms
• E atoms

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

Q10:

Diamond is one form of elemental carbon. An engagement ring contains a diamond weighing 1.5 carats (1 carat = 200 mg). How many atoms are present in the diamond?

• A
• B
• C
• D
• E

Q11:

Vitamin C is a covalent compound with the molecular formula . The recommended daily dietary allowance of vitamin C for children aged 4–8 years is mol. What is the mass of this allowance in grams?

Q12:

The approximate daily dietary requirement of the amino acid leucine, , is 15 mg/kg of body weight. For a 65 kg person, what is this requirement in millimoles?

Q13:

A 65 kg woman has mol of hemoglobin (molar mass = 64,456 g/mol) in her blood.

How many hemoglobin molecules are there?

• A
• B
• C
• D
• E

What is this quantity in grams?

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?

• 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?