Correct option (6) −15.2 kJ/mol
Explanation:
We use Hess’ Law:
∆H◦ = ∑ n ∆H◦ j,prod − ∑ n ∆H◦ j,reac
= ∆H◦ f, CaCl2(aq) + ∆H◦ f, H2O(ℓ)
+ ∆H◦ f,CO2(g) − [ ∆H◦ f, CaCO3(s) 2 + (∆H◦ f, HCl(aq)]
= −877.1 kJ/mol + (−285.83 kJ/mol)
+ (−393.51 kJ/mol) − [ −1206.9 kJ/mol + 2 (−167.16 kJ/mol)]
= −15.22 kJ/mol .