At constant temperature 2L of `N_(2)` gas at 750 mm Hg pressure I mixed with 3L of `O_(2)` gas. As a result the pressure and volume of the gas mixture are found to be 732 mm Hg and 5 L respectively. What is the initial pressure of `O_(2)` gas?

Explanation

`{:(P_(N_(2))xxV=n_(N_(2))RT),(750xx2=n_(N_(2))RT):|{:(P_(O_(2)) xxV=n_(O_(2))RT),(P_(O_(2))xx3=n_(O_(2))RT):}`
In mixture:
`PV=nRT=(n_(O_(2))+n_(N_(2)))RT=P_(O_(2))xx3+750xx2`
`732xx5=P_(O_(2))xx3+1500" "therefore P_(O_(2))=720` mm Hg.