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.What is the concentration (in mol/L) of the hydrogen peroxide solution?

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)           


Ptotal=PGas 1+PGas 2+PGas 3...Ptotal=PO2+Pwater763.6 mm Hg=PO2+23.78 mm Hg

PO2=739.82 mmHg


Ideal Gas equation: moles O2


PV=nRTn=PVRTn=739.82 mm Hg×1 atm760 mm Hg49.5 mL× 10-3LmL0.08206L·atmmol·K25°C+273.15 K

n = 1.97 x10-3 mol O2


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

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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.

What is the concentration (in mol/L) of the hydrogen peroxide solution?

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