# Problem: Hydrogen peroxide (H2O2) decomposes in the presence of a catalyst to form water and oxygen. The catalyst is added to 5.00 mL of a hydrogen peroxide solution at 25.0˚C, and 49.5 mL of gas is collected over water at a total pressure of 763.6 mmHg.How many grams of hydrogen peroxide were in the original sample?

###### FREE Expert Solution

Balanced equation: 2H2O→ 2H2O + O2

Solve for PO→ moles O → moles H2O2

Using Dalton’s Law: PO2
at 25.0°C, Pwater = 23.78 mm Hg (vapor pressure)

${\mathbit{P}}_{{\mathbf{O}}_{\mathbf{2}}}\mathbf{=}$739.82 mmHg

Ideal Gas equation: moles O2

n = 1.97 x10-3 mol O2

Mole to mole comparison: 2 moles H2O2 forms 1 mole O2

• Molar mass H2O2 = 34.02 g/mol
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###### Problem Details

Hydrogen peroxide (H2O2) decomposes in the presence of a catalyst to form water and oxygen. The catalyst is added to 5.00 mL of a hydrogen peroxide solution at 25.0˚C, and 49.5 mL of gas is collected over water at a total pressure of 763.6 mmHg.

How many grams of hydrogen peroxide were in the original sample?