Chapter 21, Problem 129SCQ

Comparing the chemistry of carbon and silicon.

(a) Write balanced chemical equations for the reactions of H₂O(ℓ) with CH₄ (forming CO₂ and H₂) and SiH₄ (forming SiO₂ and H₂).

(b) Using thermodynamic data, calculate the standard free energy change for the reactions in (a). Is either reaction product-favored at equilibrium?

(c) Look up the electronegativities of carbon, silicon, and hydrogen. What conclusion can you draw concerning the polarity of C—H and Si—H bonds?

(d) Carbon and silicon compounds with the formulas (CH₃)₂CO (acetone) and [(CH₃)₂SiO]_n (a silicone polymer) also have quite different structures. Draw Lewis structures for these species. This difference, along with the difference between structures of CO₂ and SiO₂, suggests a general observation about silicon compounds. Based on that observation, do you expect that a silicon compound with a structure similar to ethene (C₂H₄) exists?