a)
∆H⁰ = ∑n∆H⁰tw. prod. - ∑n∆H⁰tw. substr. = (∆H⁰tw.CaO(s) + 2∆H⁰tw.CO2(g)) - ∆H⁰ tw.CaCO3(s) - = (-635 kJ/mol) + (-392 kJ/mol) - (-1207 kJ/mol)) = -1029 kJ/mol + 1207 kJ/mol = +178 kJ/mol
b)
∆H⁰ = ∑n∆H⁰ tw. prod. - ∑n∆H⁰tw. substr. = 2 ∙ ∆H⁰tw.H2O(c) - (∆H⁰tw.SO2(s) + 2 ∙ ∆H⁰tw.H2S(g)) = 2 ∙ (-286 kJ/mol) – (-297 kJ/mol + 2 ∙ (-21 kJ/mol)) = -572 kJ/mol + 339 kJ/mol = -233 kJ/mol
