One mole of Phenol is warmed with sodium metal. If we assume 100% yield, volume of H₂ gas liberated at S.T.P in liters is

Phenol reacts with warm sodium metal to produce sodium phenoxide (ether) and liberates H₂ gas.

According to balanced reaction,

                 1 mol of Phenol $\to$1/2 mol of H_{2 gas}

                 And 1 mol = 22.4 L volume

So, volume of H₂ gas = $\frac{22.4}{2}$ L

                                = 11.2 L

Thus, the volume of H₂ gas liberated at STP is 11.2 L.