Some solved examples of the mole are given below, which can help you understand it more easily.
Example 1.
Determine the number of moles in 10 grams of carbon.
Solution
Step 1. The mass of carbon is given. i.e.
Mass of carbon = 10 g
Step 2. Look at the periodic table.
Molar mass of carbon = 12.011 g/mol
Step 3. Write down the formula of the mole
Mole = Mass / Molar mass
Substitute these values in the formula of mole. i.e.
Mole of carbon = 10 / 12.011 = 0.832 mol
Approximately 0.832 moles are in 10 grams of Carbon.
Example 2.
Calculate the mass of 0.8 moles of Hydrogen gas.
Solution
Step 1. Here,
A mole of Hydrogen gas (H2) = 0.8 mol
Step 2. Molar mass of H2 = (2 × 1.0078) g/mol = 2.0156 g/mol
Step 3. We have the following equation to find the mass of hydrogen gas.
Mass = Moles × Molecular weight
Put the above values in the formula of mass. i.e.
Mass = 0.8 × 2.0156 = 1.6124 grams
The mass of 0.8 moles of hydrogen gas is 1.6124 grams.