题目

向滴有酚酞的NaOH溶液中，逐渐滴入稀盐酸至过量，下面叙述正确的是（    ）             A. 溶液由红色变为无色，PH逐渐增大                    B. 溶液由无色变为红色，PH逐渐减小 C. 溶液由红色变为无色，PH逐渐减小                    D. 溶液颜色不变，PH逐渐增大 答案：【答案】C  【考点】溶液的酸碱性与pH值的关系   【解析】【解答】解：酚酞遇碱变红遇酸不变色，故在反应过程中溶液会先有红色，至恰好反应到过量时溶液会变成无色，PH会由大于7到等于7再到小于7．  故选C 【分析】酚酞试液遇酸性溶液不变色，遇碱性溶液变红，遇中性溶液不变色．可以根据The reason ____he was absent from the meeting was ____his car broke down on the way.( )A. that; becauseB. why; thatC. that; thatD. for; that