$$2C_2H_2(g) + 5O_2(g) → 4CO_2(g) + 2H_2O(l)$$
The standard enthalpy change for this reaction is:
$$\Delta H^0 = -1300 kJ$$
Under standard conditions (25°C, 1 atm), the maximum amount of useful work that can be accomplished by this reaction is given by the equation:
$$W_{max} = -\Delta H^0 = 1300 kJ$$
Therefore, the maximum amount of useful work that can be accomplished under standard conditions by this reaction when 4 mol C2H2 burned is 1300 kJ.
