Constants I Periodic Table Hydrogen peroxide (H2O2) decomposes in the presence o

Question

Constants I Periodic Table Hydrogen peroxide (H2O2) decomposes in the presence of a catalyst to form water and oxygen. The catalyst was added to 6.00 mL of a hydrogen peroxide solution at 25.0 °C, and 50.5 mL of gas was collected over water at a total pressure of 764.2 mmHg Look up the vapor pressure of water under these conditions in the table. TABLE Vapor Pressure of Water versus Temperature Temperature (°C) Pressure Temperature (°C) Pressure (mmHg) 4.58 6.54 9.21 12.79 17.55 23.78 3186 42.23 55.40 71.97 92.6 (mmHg) 118.2 149.6 187.5 233.7 289.1 355.1 433.6 525.8 633.9 760.0 10 15 20 25 30 35 40 45 50 60 65 70 75 80 85 90 95 100

Explanation / Answer

Pressure of oxygen gas = total pressure - vapour pressure of water = 764.2 - 23.78 = 740.42 mmHg

P = 740.2 / 760 = 0.974 atm

T = 25 + 273.15 = 298.15 K

R = 0.0821 L.atm.K-1.mol-1

V = 50.5 mL = 0.0505 L

n = ?

Assuming ideal gas behaviour,

Ideal gas equation,

P V = n R T
0.974 * 0.0505 = n * 0.0821 * 298.15

n = number of moles of oxygen gas = 0.00201 mol

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