Chapter 4, Problem 73QRT

Three reactions very important to the semiconductor industry are

1. (a) The reduction of silicon dioxide to crude silicon,

   SiO₂(s) + 2 C(s) → Si(s) + 2 CO(g) Δ_rH° = 689.9 kJ/mol

2. (b) The formation of silicon tetrachloride from crude silicon,

   Si(s) + 2 Cl₂(g) → SiCl₄(g) Δ_rH° = −657.01 kJ/mol

3. (c) The reduction of silicon tetrachloride to pure silicon with magnesium,

   SiCl₄(g) + 2 Mg(s) → 2 MgCl₂(s) + Si(s) Δ_rH° = −625.6 kJ/mol

Calculate the overall enthalpy change when 1.00 mol sand, SiO₂, changes into very pure silicon by this series of reactions.