Question

Determine which of the following reactions at constant pressure represent surrounding that do work on the system :

I. 4NH3 (g) + 7O2 (g) $\longrightarrow$ 4NO2 (g) + 6H2O (g)

II. CO (g) + 2H2 (g) $\longrightarrow$ CH3OH ($\mathcal{l}$)

III. C (s, graphite) + H2O (g) $\longrightarrow$ CO (g) + H2 (g)

IV. H2O (s) $\longrightarrow$ H2O ($\mathcal{l}$)

• A. III, IV
• B. II and III
• C. II, IV
• D. I and II, IV

Answer 1

Answer: (D)

I and II, IV

Answer 2

w = – Pext. $\Delta$V = – $\Delta$ngRT and $\Delta$ng is–Ve for I and II

also $\Delta$V = – ve for IV