The number of mole of a molecule is defined as its mass per molar mass. using # mol = n, mass = m and molar mass = m and given that n = m m , rearrange this expression for (a) m = ? (b) m = ? (c) if n = 0.0021 mol and m = 44 g/mol; what is the value of m?

Given:
n = 0.0021 mol
M = 44 gram/mol

Required: m or the mass of the molecule

Solution:

M = m/n

Rearranging the expression,

m = M x n
m = 44 g/mol x 0.0021 mol

Evaluating the expression and cancelling units, we obtain,

m = 0.0924 grams

M is the molar mass. This value is very useful in chemistry calculations especially in calculating the amounts of reactants and products for a chemical reaction.