To calculate the mass percent or weight percent of a solution, you must divide the mass of the solute by the mass of the solution (both the solute and the solvent together) and then multiply by 100 to change it into percent.
<em>W% = [(W of solute NaF)/(W of solution)] x 100.</em>
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W of solute NaF = 65.4 g.
W of solution = W of solute NaF + W of water = 65.4 g + 125.1 g = 190.5 g.
∴ W% = [(W of solute NaF)/(W of solution)] x 100 = [(65.4 g)/(190.5 g)] x 100 = 34.33 %.
