题干

已知镁可以和热水反应[Mg+2H2O Δ__ Mg(OH)2+H2↑]并放出热量,待反应完全后,趁热滴入几滴无色的酚酞试液,溶液呈红色,但随着温度的降低,红色渐渐褪去,直至无色.以下判断不合理的是(   )

A:温度降低,Mg(OH)2的溶解度减小

B:温度降低,溶液的pH值变小

C:酚酞试液与空气中的二氧化碳反应而失效

D:溶液中的Mg(OH)2与空气中的二氧化碳反应

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答案(点此获取答案解析)

C

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