0.75 mole of solid `A_(4)` and 2 mole of gaseous `O_(2)` are heated to react completely in a sealed bottle to produce gaseous compound `A_(3)O_(n)`. After the compound is formed, the vessel is brought to initial temperature, the pressure is found to half of initial pressure. The value of n is ________.

Explanation

`underset(`{:(i nitial mol),(Fi nal mol):}](0.75)(2)(0) `)(X_(4)+O_(2)toY)`
Initial pressure is due to `O_(2)` (2 mol), because `X_(4)` is solid and final pressure is due to Y only (a mol). Temperature remains constant.
Now, `Pprop" mol of "O_(2)prop2`
`(P)/(2)prop" mol of "Ypropa`
In other words, only 1 " mol of "Y is formed.
The mol ratio of `X_(4):O_(2)` in `Y=0.75:2`
Ratio of atoms of X and O in `Y=4xx0.75:2xx2=3:4`
Thus, Y is `X_(3)O_(4)`