A 2.0 L container at `25^(@)C` contain 1.25 mol of `O_(2)` and 3.2 mol of C.
(a) What is the initial pressure in the flask ?
(b) If the carbon and oxygen react as completely as possible to form `CO,` what will be the final pressure in the container?

Explanation

(a) V=2.0 L, T=298 K, n=1.25 mol (because only gas will exert pressure). Hence,
PV=nRT or `P=(nRT)/(V)=((1.25" mol")(0.0821" L atm "K^(-1)mol^(-1))(298 K)/(2.0" L")=15.3" atm"`
(b) The reaction will be :`C(s)+(1)/(2)O_(2)(g) to CO(g)`
As 1 mol of C reacts with `(1)/(2)` mol of `O_(2)`, the limiting reactant will be 1.25 mol of `O_(2)`. Thus, `(1)/(2)` mol of `O_(2)` produces CO=1 mol.
`:.1.25` mol of `O_(2)` will produce CO=2.50 mol.
Now, n(gaseous)=2.50 mol. Hence,
`P=(nRT)/(V)=((2.50" mol")(0.0821" L atm "K^(-1)mol^(-1)(298"K"))/(2.0" L ")=30.6" atm "`.