The gas liberated when sodium react with water is
hydrogen gas.
When sodium reacts with water, a gas called hydrogen gas (H2) is liberated. The reaction can be represented as follows:
2 Na + 2 H2O → 2 NaOH + H2
In this reaction, sodium (Na) reacts with water (H2O) to form sodium hydroxide (NaOH) and release hydrogen gas (H2).