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, NH24?

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 LiH units. What is the relative formula mass of lithium hydride?

Q5:

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

  • A𝑀=𝑚𝑛
  • B𝑛=𝑚𝑀
  • C𝑚=𝑀
  • D𝑚=𝑛𝑀
  • E𝑛=𝑚+𝑀

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 112th 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 Au atoms in this quantity of gold.

  • A4.41×10 atoms
  • B7.50×10 atoms
  • C6.70×10 atoms
  • D3.63×10 atoms
  • E4.83×10 atoms

Q9:

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

  • A6.02×10
  • B7.24×10
  • C6.24×10
  • D6.63×10
  • E1.51×10

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?

  • A1.5×10
  • B7.5×10
  • C2.6×10
  • D1.0×10
  • E1.5×10

Q11:

Vitamin C is a covalent compound with the molecular formula CHO686. The recommended daily dietary allowance of vitamin C for children aged 4–8 years is 1.42×10 mol. What is the mass of this allowance in grams?

Q12:

The approximate daily dietary requirement of the amino acid leucine, CHNO6132, is 15 mg/kg of body weight. For a 65 kg person, what is this requirement in millimoles?

Q13:

A 65 kg woman has 8.9×10 mol of hemoglobin (molar mass = 64,456 g/mol) in her blood.

How many hemoglobin molecules are there?

  • A5.4×10
  • B5.4×10
  • C5.4×10
  • D5.4×10
  • E5.4×10

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.

  • A1.661×10
  • B6.626×10
  • C1.381×10
  • D6.022×10
  • E2.998×10

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?

  • A8.61×10moles
  • B8.61×10moles
  • C8.61×10moles
  • D8.61×10moles
  • E8.61×10moles

Q16:

As a molar percentage, 80.3% of a boron sample is 11B and the remainder is 10B. What is the average molar mass of the boron sample?

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