Answer: the sum of the partial pressures of the individual gases.
Explanation:
According to Dalton's Law of partial pressure, the total pressure of a mixture of gases is equal to the sum of the partial pressures which each individual gas would exert if it were confined alone in the volume occupied by the mixture.
Hence, Ptotal = P1+ P2
where Ptotal is the total pressure
P1 and P2 are the partial pressures exerted seperately by the individual gases 1 and 2 that make up the mixture.
