The total pressure of the mixture of gases is equal to the sum of the pressure of each gas as if it is alone in the container. The partial pressure of a component of the mixture is said to be equal to the product of the total pressure and the mole fraction of the component in the mixture.
Partial pressure of hydrogen gas = 1.24 atm x .25 = 0.31 atm
Partial pressure of the remaining = 1.24 atm x (1-.25) = 0.93 atm
