2Na(s)+2H2O(l)⟶2NaOH(aq)+H2(g) 1 mole of Na=23g of Na 4 moles of Na=92g of Na 2 moles of Na reacts with 2 moles of H2O to form 1 mole of H2 . 4 moles of Nawill react with 4 moles of H2O to form 2 moles of H2. Work done by expansion of gas is given by −p∆V p∆V=∆ngRT At constant external pressure, ∆V=VH2−0=VH2 p∆V=∆ngRT p∆V=∆ngRT=2×8.314×300=4.98kJ Therefore, the work done is 4988.4J . Since it is work of expansion so will be with negative sign (−4988.4J) .