✔ 最佳答案
(1)
The ionic compound NH4OH does not exist. It is possible to obtain a solution containing NH4+(aq) and OH-(aq), and this is a mixture. However, when the solution is evaporated, no NH4OH is obtained, but it is decomposed to give NH3(g) and water vapour.
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(2)
MnO4-(aq) ion would not be discharged in electrolysis. When a solution of MnO4-(aq) ion is electrolysed, OH-(aq) would be preferentially discharged at the anode because OH-(aq) ion is oxidized much more readily than MnO4-(aq).
（Reference: SO42-(aq) and NO3-(aq) are also not discharged at the anode in electrolysis.）
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(3)
Since HCO3-(aq) ion is produced from a very weak acid H2CO3(aq), HCO3-(aq) ion would therefore react reversibly with water to form back to H2CO3(aq) and give OH-(aq).
HCO3-(aq) + H2O(l) ≒ H2CO3(aq) + OH-(aq) ... (*)
However, HCO3-(aq) can also partially ionized in water to give H+(aq).
HCO3-(aq) ≒ CO32-(aq) + H+(aq) ... (**)
The tendency of giving OH-(aq) in (*) is greater than the tendency of giving H+(aq) in (**). Therefore, HCO3-(aq) give a slightly alkaline solution. At room temperature, 0.1 M NaHCO3 has a pH of about 8.4.
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(4)
CO32-(aq) ion is produced from the ionization of HCO3-(aq) ion, which is a weak alkali. Therefore, CO32-(aq) has a great tendency to react with water to change back to HCO3-(aq) ion and give OH-(aq).
CO32-(aq) + H2O(l) ≒ HCO3-(aq) + OH-(aq)
Na2CO3 is an alkali. At room temperature, 0.1 M Na2CO3 solution has a pH of about 11.6.
