mass percent?

Question

Mass percent is grams of solute over liters of solution (hydrogen peroxide)

I know i have .46 moles in .00872 liters and the density is 1.00g/ml

what is the %m/m?

Answer 1

Mass percent is NOT grams of solute over liters of solution.
Mass percent is grams of solute over total mass of the solution.
If the density of your solution is 1.00g/ml, the total mass of the solution is 0.00872L*1.00g/ml = 8.72ml*1.00g/ml = 8.72g.
If the molar mass of the solute is X (g/mol), the mass of the solute would be 0.46*X (unit gram), so the mass percent would be 0.46*X/8.72.