Question: how to calculate number of moles from weight percent?
Answer: Divide the molecular weight into the weight of solute in the solution to find the number of moles: 2.7 g ÷ 58 g/mole = 0.047 moles. Divide by the volume of the solution to find molarity: M = (0.047 moles ÷ 0.09 liters) = 0.52 moles/liter.