The intermediate SiH 2 is formed in the thermal decomposition of silicon hydrides. Calculate Δ f H° of SiH 2 from the following reactions: Si 2 H 6 (g) + H 2 (g) → 2SiH 4 (g); ΔH° = -11.7 kJ/mol SiH 4

Question

The intermediate SiH 2 is formed in the thermal decomposition of silicon hydrides. Calculate Δ f H° of SiH 2 from the following reactions: Si 2 H 6 (g) + H 2 (g) → 2SiH 4 (g); ΔH° = -11.7 kJ/mol SiH 4 (g) → SiH 2 (g) + H 2 (g); ΔH° = +239.7 kJ/mol Δ f H°, Si 2 H 6 (g) = +80.3 kJ/mol

TestHub · Accepted Answer

From the first reaction, we calculate the enthalpy of formation for SiH_₄:

2Δ_f H(SiH₄) = -11.7 + 80.3 = 68.6

So, Δ_f H(SiH₄) = 34.3 kJ/mol.

From the second reaction, we calculate the enthalpy of formation for SiH_₂:

Δ_f H(SiH₂) = Δ_f H(SiH₄) + 239.7 = 34.3 + 239.7 = 274 kJ/mol.

This corresponds to option (d).

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