9. Suppose two gases in a container have a total pressure of 1.20 atm. What is the pressure of gas B if the partial pressure of gas A is 0.75 atm?

1 Answer
anor277
Jan 26, 2017

#P_B=0.45*atm#

Explanation:

Dalton's Law of partial pressure holds that in a gaseous mixture, the pressure exerted by a component is the same as the pressure it would exert if it ALONE occupied the container. The total pressure is the sum of the individual partial pressure.

i.e. #P_"Total"=P_1+P_2+P_3.........#

And here #P_"Total"=1.20*atm=P_A+P_B=0.75*atm+P_B#,

i.e. #P_B=1.20*atm-0.75*atm=??*atm.#

Note that we can use this law to access the number of moles of each gas, given that #P=(nRT)/V#,

i.e. #P_"Total"=(RT)/V{n_1+n_2+...........n_n}#, where #n_i# is the number of moles of gas #i#.

And we can show that:

#P_i/P_"Total"=n_i/n_"Total"#,

i.e. partial pressure is equivalent to mole fraction.

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