Question

Hydrogen peroxide is a powerful oxidizing agent; it is used in concentrated solution in rocket fuel and in dilute solution in hair bleach. An aqueous solution is 29% by mass and has a density of 1.23 g/ml. Calculate the molarity of H2O2. Enter to 1 decimal place.

Answer 1

Let volume of solution be 1 L
volume , V = 1 L
= 1*10^3 mL


density, d = 1.23 g/mL
use:
mass = density * volume
= 1.23 g/mL *1*10^3 mL
= 1230.0 g
This is mass of solution
mass of H2O2 = 29.0 % of mass of solution
= 29.0*1230.0/100
= 356.7 g

Molar mass of H2O2,
MM = 2*MM(H) + 2*MM(O)
= 2*1.008 + 2*16.0
= 34.016 g/mol


mass(H2O2)= 356.7 g

use:
number of mol of H2O2,
n = mass of H2O2/molar mass of H2O2
=(356.7 g)/(34.016 g/mol)
= 10.49 mol
volume , V = 1 L


use:
Molarity,
M = number of mol / volume in L
= 10.49/1
= 10.49 M
Answer: 10.5 M