Help with chemistry question

Question

Given below are the reaction and the standard enthalpy change of formation values:

SiH‎‎_4(g) + 2 ‎‎O_2(g) ➜ S‎‎iO_2(s) + 2 H‎‎₂O_(l)  Δ‎‎H_rxn= –1,51‎‎6.8 kJ

ΔH°f (kJ/‎‎mol)
S‎‎iO2(s)	–91‎‎0.9
H2‎‎O(l)	–28‎‎5.8

 

What is the ΔH°_f for Si‎‎‎H_4(g)?

Select one:

a.

320.1 kJ/mol

b.

–320.1 kJ/mol

c.

34.3 kJ/mol

d.

–34.3 kJ/mol

Answer 1

SiH‎‎_4(g) + 2 ‎‎O_2(g) ➜ S‎‎iO_2(s) + 2 H‎‎₂O_(l) ...  Δ‎‎H_rxn= –1,51‎‎6.8 kJ

∆Hrxn = ∑n∆H_f products - ∑n∆H_f reactants

-1516.8 = [(-910.9) + (2x-285.8)] - [∆H_f SiH₄ + 0]

-1516.8 = -1482.5 - ∆H_f SiH₄

∆H_f SiH₄ = +34.3 kJ/mol (Answer c)