A vessel contains `14` g (`7` moles ) of hydrogen and `96` g (`3`moles) of oxygen at `STP`. Chemical reaction is induced by passing electric spark in the vessel till one of the gases is consumed. The temperature is brought back to it's starting value `273 K` .The pressure in the vessel is-

Options

A. `0.1`atm
B. `0.2` atm
C. `0.3` atm
D. `0.4` atm

Answer

A

Explanation

When electric spark is passed, hydrogen reacts with oxygen to form water `(H_(2)O)`. Each gram of hydrogen reacts with eight grams of oxygen. Thus `96` g of oxygen will be totally consumed together with `12` g of hydrogen.
The gas left in the vessel will be `2`g of hydrogen i.e. number of moles `mu = (2)/(2) = 1`.
Using `PV= muRT implies P prop mu implies (P_(2))/(P_(1)) = (mu_(2))/(mu_(1)) implies (P_(2))/(1) implies 0.1 "atm"`