Daltons Law

by Dasa . 27 No 2021
Hydrogen Oxygen

When we place two gases in a container, the total pressure exerted by the mixture is

= Sum of partial pressure of each gas

When we place 1 mol of Oxygen & 1 mol of Hydrogen in a container

Ptotal=PO2+PH2P_{total} = P_{O_{2}} + P_{H_{2}}

The ideal gas law

PV=nRTP * V = n * R * T

P=nRTVP = \dfrac{n * R * T} {V}

Where,
P - Pressure exerted by the gas in inHginHg
n - Amount of gas in lbmollb-mol
R - Universal gas constant = 21.85 inHgft3lbmoloR\dfrac{inHg*ft^{3}}{lb-mol* ^oR}
T - Absolute temperature of the gas in oR^oR
V - Volume of the gas in ft3ft^3

Partial Pressure of gas:
lb-mol of the gas (lb-mol):
Rankine temperature the gas (°R):
Partial Pressure (mmHg):

Example:

At 68° F, consider placing 1 lb of Hydrogen gas (H2H_{2}) and 1 lb of Oxygen gas (O2O_{2}) in a container of 15 ft3ft^3.

Click here to get atomic mass in g/mol, for various elements.

H = 1.008 gram/mol
H2 = 2.016 gram/mol
= 2.016 ÷ 454 lb/mol
= 0.00444 lb/mol

O = 15.999 gram/mol
O2 = 31.998 gram/mol
= 31.998 ÷ 454 lb/mol
= 0.07048 lb/mol

Then,

1 lb of H2H_{2} = 1 ÷ 0.00444 mol
= 225.225 mol
= 225.225 ÷ 454 lb-mol
= 0.496 lb-mol

1 lb of O2O_{2} = 1 ÷ 0.07048 mol
= 14.188 mol
= 14.188 ÷ 454 lb-mol
= 0.03125 lb-mol

T = 68° F
= 68 + 459.67 ° R
= 527.67° R

Partial Pressure exerted by H2

PH2=0.49621.85527.6715P_{H_{2}} = \dfrac{0.496 * 21.85 * 527.67} {15}
=381.25mmHg= 381.25\,mmHg

Partial Pressure exerted by O2

PO2=0.0312521.85527.6715P_{O_{2}} = \dfrac{0.03125 * 21.85 * 527.67} {15}
=24.02mmHg= 24.02\,mmHg

Total Pressure exerted

= 381.25 + 24.02
= 405.27 mmHg


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