Question

(1) (12 pts) When H2S(g) is bubbled into aqueous nitric acid solutions, S(s), NO2(g), NO(g), N2(g), and NH4 + (aq) are all formed.

(a) (8 pts) Write the four balanced chemical reactions (using only electrically neutral species) that describe this process.

(b) (4 pts) For each reaction in part (a), evaluate the number of moles of electrons transferred per mole of H2S(g).

Answer 1

Part (a).

(i) H₂S(g) + 2HNO₃(aq) ----> S(s) + 2NO₂(g) + 2H₂O(l)

(ii) 3H₂S(g) + 2HNO₃(aq) ----> 3S(s) + 2NO(g) + 4H₂O(l)

(iii) 5H₂S(g) + 2HNO₃(aq) ----> 5S(s) + N₂(g) + 6H₂O(l)

(iv) 4H₂S(g) + HNO₃(aq) + H⁺(aq) ----> 4S(s) + NH₄⁺(aq) + 3H₂O(l)

(b) In each case, the no. of moles of electrons transferred per mole of H₂S = 0 - (-2) = 2