试题与答案

推理是化学学习中常见的思维方法。下列推理正确的是( ) A.碱性溶液能使酚酞试液

题型:选择题

题目:

推理是化学学习中常见的思维方法。下列推理正确的是(      )

A.碱性溶液能使酚酞试液变红,滴入酚酞试液后变红的溶液一定呈碱性

B.锌和铜均是金属,锌与稀硫酸反应生成氢气,则铜也能与稀硫酸反应生成氢气

C.酸能使石蕊试液变红,CO2也能使紫色的石蕊试液变红,所以CO2是酸

D.溶液中有晶体析出,其溶质质量减小,所以溶质的质量分数一定减小

答案:

答案:A

题目分析:A、碱性溶液能使酚酞试液变红,滴入酚酞试液后变红的溶液一定呈碱性,但不一定是碱的溶液;

B、锌和铜均是金属,锌与稀硫酸反应生成氢气,但铜不能与稀硫酸反应生成氢气,因为铜的活动性弱与氢;

C、酸能使石蕊试液变红,二氧化碳通入石蕊试液后,也能变红,但二氧化碳不是酸,是二氧化碳与水反应生成的碳酸使石蕊试液变红的;

D、溶液中有晶体析出,其溶质质量减小,但其溶质的质量分数不一定减小,如饱和溶液在恒温蒸发水分时,有晶体析出,但溶液的溶质质量分数不变。

选A。

点评:紫色石蕊试液是酸碱指示剂,遇到酸性物质变红,遇到碱性物质变蓝;溶解度是温度的函数,饱和溶液在恒温蒸发水分时,有晶体析出,但溶液的溶质质量分数不变。

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