Question

Calculate the standard molar entropy change (∆S°) at 298 K for the reaction: 2H2 (g) + O2 (g) → 2H2O (l) given that the standard molar enthalpy change (∆H°) for this reaction is -572 kJ/mol.

Answer 1

To calculate the standard molar entropy change  S  for the reaction, we can use the Gibbs free energy equation:G = H - TSWhere G is the standard Gibbs free energy change, H is the standard enthalpy change, T is the temperature in Kelvin, and S is the standard entropy change.At equilibrium, the Gibbs free energy change is zero:0 = H - TSWe are given the standard molar enthalpy change  H  as -572 kJ/mol and the temperature  T  as 298 K. We can rearrange the equation to solve for the standard molar entropy change  S :S = H / TFirst, we need to convert the enthalpy change from kJ/mol to J/mol:H = -572 kJ/mol   1000 J/1 kJ  = -572,000 J/molNow, we can calculate the standard molar entropy change:S =  -572,000 J/mol  /  298 K  = -1919.46 J/molKThe standard molar entropy change for the reaction is approximately -1919.46 J/molK.