Question

A "shielding gas" mixture of argon and carbon dioxide is sometimes used in welding to improve the strength of the weld. if a gas cylinder of this two-part mixture was at 4.0 atm pressure and this mixture was 90.% argon, what would be the pressure due to the carbon dioxide gas component?

Answer 1

Dalton's Law of Partial Pressures, commonly applied to ideal gases, explains that the partial pressures of individual, non-reacting gases are equal to the total pressure exerted by the gas mixture. The given gas mixture composed of 90% argon and 10% carbon dioxide has the following partial pressures: 3.6 atm for argon and 0.4 atm for carbon dioxide (answer).

Answer 2

Answer is: the pressure due of carbon dioxide gas is 0.4 atm.

p(mixture) = 4.0 atm; mixture of argon and carbon dioxide gas.

ω(Ar) = 90% ÷ 100%.

ω(Ar) = 0.9; percentage of argon gas in mixture.

p(Ar) = 0.9 · 4.0 atm.

p(Ar) = 3.6 atm; pressure of argon gas.

The total pressure of an ideal gas mixture is the sum of the partial pressures of the gases in the mixture.

p(mixture) = p(Ar) + p(CO₂).

p(CO₂) = 4 atm - 3.6 atm.

p(CO₂) = 0.4 atm; pressure of carbon dioxide gas.