Chemistry: Molar Mass Calculation Explained

How do we calculate the mass of a certain number of moles of a compound?

For example, what is the mass of 1.50 mol of ammonium nitrate?

How do we determine the number of moles in a given mass of a compound?

For instance, how many moles of sodium bicarbonate are in a 101.5-g sample?

Answer:

The mass of 1.50 mol of ammonium nitrate is 120.06 grams, and there are 1.208 moles of sodium bicarbonate in a 101.5 g sample.

Explanation:

(a) The molar mass of ammonium nitrate (NH4NO3) is approximately 80.04 g/mol. To calculate the mass of a certain number of moles, we multiply the number of moles by the molar mass.1.50 mol of ammonium nitrate x 80.04 g/mol = 120.06 g. Therefore, 1.50 mol of ammonium nitrate has a mass of 120.06 grams.

(b) The molar mass of sodium bicarbonate (NaHCO3) is approximately 84.007 g/mol. To determine the number of moles in a given mass, we divide the mass by the molar mass. 101.5 g / 84.007 g/mol = 1.208 mol. Thus, there are 1.208 moles of sodium bicarbonate in a 101.5 g sample.