Chemistry 112

Example

Which is the stronger base: solid sodium hydroxide or solid sodium hydride (NaH)?

NaOH is a strong base and NaH is an uncommon compound so could be strong or weak. The context of the question suggests that NaH is also a strong base.

Use thermodynamic data to find ΔG° for each acid/base reaction. The more negative ΔG° is the stronger base.

NaOH:

NaOH(s) → Na+(aq) + OH(aq)

ΔGf°(NaOH(s)) = –379.5 kJ/mol

ΔGf°(Na+(aq)) = –261.9 kJ/mol

ΔGf°(OH(aq)) = –157.2 kJ/mol

ΔG° = [–261.9 + (–157.2)] – [–379.5] = –39.6 kJ/mol

 

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