CE Chemistry IV

No. of moles of H2SO4 = MV = 0.1 x (40/1000) = 0.004 mol
No. of moles of NH3 = MV = 0.4 x (20/1000) = 0.008 mol
Mole ratio H2SO4 : NH3 = 0.004 : 0.008 = 1 : 2
Hence, the equation for the reaction is
H2SO4 + 2NH3 → (NH4)2SO4

When the reaction is completed, all the H2SO4 and NH3­ are reacted. The resulting solution is a solution of (NH4)2SO4 which contains NH4+ and SO42- ions.

☺ NH4+ ion is formed from the ionization of NH3 in water. Since NH3 is a weak base, its ionization in water to give NH4+ is a reversible reaction. Therefore, NH4+ can be reversibly dissociated back to NH3 at give a slightly acidic solution.
NH4+(aq) ≒ NH3(aq) + H+(aq)

☻ SO42- ion is formed from the ionization of H2SO4 in water. Since CH3COOH is a strong acid, its ionization in water to give SO42- completes (irreversible). Therefore, SO42-(aq) can hardly formed back to H2SO4.

Combine the above two effects, the resulting solution is slightly acidic.

2008-04-11 23:03:25 補充：
Since this is a CE question, it is NOT necessary to calculate the pH of the solution.