What is the relationship between the moles of solute and the mass of solute?

the molar mass of the solute. For example, if I had 7 moles of solute and the molar mass of the solute was 3g, then my mass of solute would by 21g. BUT, if you are talking about moles of solute and kilograms of solvent, then the units (and derived terms) are molality (unit is a 1 molal).