How to determine the mass fraction of a substance?

The mass fraction of a substance is determined by the formula

v = m / mtot., where mt is the mass of that part of the substance, the mass fraction of which needs to be known; mtot. – the total mass of the substance. If the mass fraction is determined in%, then the formula takes the form

v = m / mtot. * 100%

For example: Given 500 grams of solution in which 30 grams of salt. Determine the mass fraction of salt in the solution.

v = 30/500 * 100% = 6%

Answer: the mass fraction of salt in the solution is 6%