Acontainer holds a mixture of two gases at the partial pressures of gas a and gas b, respectively, are and if of a third gas is added with no change in volume or temperature, what will the total pressure become?

The total pressure will be the sum of  the partial pressure of these three gases.

Explanation:

According to Dalton law of partial pressure,

The total pressure exerted by mixture of gases is equal to the sum of partial pressure of the individual gas.

This expression can be written as,

P(total) = P₁ + P₂ + P₃ + Pₙ

For example:

If the pressure of A is 2 atm and Partial pressure of B is 4 atm the total pressure will be,

P(total) = P₁ + P₂

P(total) = 2 atm + 4atm

P(total) = 6 atm

when third gas is added which exert the partial pressure of 4 atm,

Then total pressure will becomes,

P(total) = P₁ + P₂ + P₃

P(total) = 2 atm + 4atm + 4 atm

P(total) = 10 atm