Moles and molar mass practice problems

Chemistry Unit 4. Try each one, then open the worked solution. The Credit Sprint app generates unlimited new versions with fresh numbers.

Problem 1.

How many moles are in 28 g of H₂O? (Molar mass 18.02 g/mol.)

Show solution

n = m ÷ M = 28 ÷ 18.02 = 1.55 mol.

Problem 2.

How many moles are in 90 g of CaCO₃? (Molar mass 100.09 g/mol.)

Show solution

n = m ÷ M = 90 ÷ 100.09 = 0.899 mol.

Problem 3.

How many moles are in 69 g of NaCl? (Molar mass 58.44 g/mol.)

Show solution

n = m ÷ M = 69 ÷ 58.44 = 1.18 mol.

Problem 4.

How many moles are in 74 g of H₂SO₄? (Molar mass 98.08 g/mol.)

Show solution

n = m ÷ M = 74 ÷ 98.08 = 0.754 mol.

Problem 5.

How many moles are in 12 g of NaOH? (Molar mass 40 g/mol.)

Show solution

n = m ÷ M = 12 ÷ 40 = 0.3 mol.

Problem 6.

How many moles are in 75 g of KCl? (Molar mass 74.55 g/mol.)

Show solution

n = m ÷ M = 75 ÷ 74.55 = 1.01 mol.