Concentrations of Solutions Molarity Percent by Mass Stoichiometry

Household hydrogen peroxide is an aqueous solution containing 3.0% hydrogen peroxide by mass. What is the molarity of this solution? (Assume a density of 1.01 g/mL.)

1. Calculate Moles H2O2 in Solution

3.0% H2O2 by mass = (grams H2O2)/ (grams solution) x 100

assume 100 grams of solution

3.0% H2O2 by mass = (grams H2O2)/ (100 g solution) x 100
0.030 = (grams H2O2)/(100 g solution)
3.0 = grams H2O2
(3.0 grams H2O2)/1 x (1 mole H2O2)/(34.02 g H2O2) = 0.088 moles H2O2

2. Calculate Liters of Solution

(100 g sol’n)/1 x (1 mL sol’n)/(1.01 g sol’n) x (1 L sol’n)/(1000 mL sol’n) = 0.0990 L sol’n

3. Calculate Molarity H2O2(aq)

Molarity H2O2 = (mol H2O2)/(L solution) = (0.088 mol H2O2)/(0.099 L sol’n) = 0.89 M

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