To calculate the Gibbs free energy change G for the reaction of hydrogen gas H2 and chlorine gas Cl2 to form hydrochloric acid 2HCl at standard conditions 298 K and 1 atm , we can use the following equation:G = H - TSwhere H is the change in enthalpy, T is the temperature in Kelvin, and S is the change in entropy.First, we need to find the standard enthalpy change H and standard entropy change S for the reaction. These values can be found in standard thermodynamic tables.For the given reaction:H2 g + Cl2 g 2HCl g The standard enthalpy change H and standard entropy change S are as follows:H H2 = 0 kJ/mol since it is an element in its standard state H Cl2 = 0 kJ/mol since it is an element in its standard state H HCl = -92.3 kJ/molS H2 = 130.7 J/molKS Cl2 = 223.1 J/molKS HCl = 186.8 J/molKNow, we can calculate the changes in enthalpy H and entropy S for the reaction:H = [2 * H HCl ] - [H H2 + H Cl2 ] = 2 * -92.3 - 0 + 0 = -184.6 kJ/molS = [2 * S HCl ] - [S H2 + S Cl2 ] = 2 * 186.8 - 130.7 + 223.1 = 373.6 - 353.8 = 19.8 J/molKNow, we can calculate the Gibbs free energy change G at 298 K:G = H - TS = -184.6 kJ/mol - 298 K * 19.8 J/molK / 1000 J/kJ = -184.6 kJ/mol - 5.9 kJ/mol = -190.5 kJ/molSo, the Gibbs free energy change for the reaction of hydrogen gas H2 and chlorine gas Cl2 to form hydrochloric acid 2HCl at standard conditions 298 K and 1 atm is -190.5 kJ/mol.