Mg(OH)2在水中达到溶解平衡：Mg(OH)2(s)
Mg2＋＋2OH－，下列哪种情况可使Mg(OH)2(s)的量减少( )
A．加入MgCl2溶液
B．加入少量NaOH
C．加入NH4NO3溶液
D．加入K2S溶液
答案：C
A使[Mg2＋]增大，B使[OH－]增大，均使平衡逆向移动，Mg(OH)2(s)的量增加，加入K2S溶液，S2－水解呈碱性，抑制Mg(OH)2固体溶解；加入NH4NO3，NH
与OH－结合生成NH3·H2O，使[OH－]减小，平衡向右移动，促进Mg(OH)2(s)溶解。
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