Question

A mixture of krypton and oxygen gases, in a 9.02 L flask at 24°C, contains 33.5 grams of krypton and 8.39 grams of oxygen. The partial pressure of oxygen in the flask is atm and the total pressure in the flask is

Answer 1

Answer -

Given,

Volume of Flask = 9.02 L

Temperature = 24 ^$\degree$ C or 297.15 K [0°C + 273.15 = 273.15K]

mass of Krypton = 33.5 g

molar mass of Krypton = 83.798 u

mass of Oxygen gas = 8.39 g

molar mass of O₂ = 32 u

Partial Pressure of Oxygen Gas = ?

Total Pressure = ?

According to Dalton's Law,

Partial Pressure = Mole Fraction * Total Pressure

Also,

Molar Fraction = Moles/ Total Moles

Partial Pressure = (Moles/ Total moles) * Total Pressure --------A

Also,

Moles = Mass/Molar Mass

Moles of Krypton = 33.5 g/83.798 u

Moles of Krypton = 0.4 mol

Moles of O₂ = 8.39g /32 u

Moles of O₂ = 0.26 mol

Total Moles = Moles of Krypton + Moles of Oxygen gas

Total Moles = 0.4 mol + 0.26 mol = 0.66 mol

Now,

We know that,

PV = nRT

where, P = Pressure

V = Volume

n = mole

R = Gas Constant (0.082057 L atm K⁻¹mol⁻¹)

T = Temperature in K

Put the values,

P_total * V = n_total *R*T

P_total * 9.02 L = 0.66 mol *0.082057 L atm K⁻¹mol⁻¹ *297.15 K

P_total = 1.78 atm [Answer]

Put the values in A,

Partial Pressure = (Moles/ Total moles) * Total Pressure

Partial Pressure of Oxygen gas = (0.26 mol/ 0.66 mol) * 1.78 atm

Partial Pressure of Oxygen gas = 0.70 atm [Answer]