Silicon forms a series of compounds analogous to the alkanes and having the general formula Si_nH_2n+2. The first of these compounds is silane, SiH₄, which is used in the electronics industry to produce thin ultrapure silicon films. SiH₄(g) is somewhat difficult to work with because it is pyrophoric at room temperature—meaning that it bursts into flame spontaneously when exposed to air.

(a) Write an equation for the combustion of SiH₄(g). (The reaction is analogous to hydrocarbon combustion, and SiO₂ is a solid under standard conditions. Assume the water produced will be a gas.)

(b) Use the data from Appendix E to calculate ΔS° for this reaction.

(c) Calculate ΔG° and show that the reaction is spontaneous at 25°C.

(d) Compare ΔG° for this reaction to the combustion of methane. (See the previous problem.) Are the reactions in these two exercises enthalpy or entropy driven? Explain.

Data from previous problem

Natural gas (methane) is being used in experimental vehicles as a clean-burning fuel.

Write the equation for the combustion of CH₄(g), assuming that all reactants and products are in the gas phase.

Use data from Appendix E to calculate ΔS° for this reaction.

Calculate ΔG° and show that the reaction is spontaneous at 25°C.