Question

Using values of ΔG°_f, calculate ΔG°_rxn for the following reaction. Is the reaction product-favored or reactant-favored?

SiCl₄(g) + 2 Mg(s) → 2 MgCl₂(s) + Si(s)

	ΔG°f (kJ/mol)
HgS(s)	-50.6
SO2(g)	-300.13
H2S(g)	-33.56
H2O(ℓ)	-228.59
SiCl4(g)	-622.76
MgCl2(s)	-591.59

____ kJ/mol?

product-favored or reactant-favored?

Answer 1

Reaction taking place is:

SiCl₄(g) + 2Mg(s) --> 2MgCl₂(s) + Si(s)

dG_rxn = dG_prod - dG_react

dG_prod = 2*dG_MgCl2 + dG_Si = 2*(-591.59) + 0 = -1183.18 kJ

dG_react = dG_SiCl4 + 2*dG_Mg = -622.76 + 2*0 = -622.76 kJ

So,

dG_rxn = -1183.18 - (-622.76) = -560.42 kJ

Since dG_rxn < 0, this means the reaction is spontaneous and is hence product favored.

Hope this helps !