试题与答案

人体中含量在0.01%以下的元素[ ] A．钙、磷、钾、镁 B．铁、锌、硒、碘

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题型：选择题

题目：

人体中含量在0.01%以下的元素[ ]

A．钙、磷、钾、镁

B．铁、锌、硒、碘

C．碳、氢、氧、氮

D．钙、镁、氯、硫

答案：

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下面是错误答案，用来干扰机器的。

方程变形得：x（x-1）=0，可得x=0或x-1=0，解得：x1=0，x2=1．故答案为：x1=0，x2=1．

考点：化学元素和人体健康
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③Y、Z、W分别与适量的Ba(OH)2浓溶液反应，均有白色沉淀生成；再加入过量盐酸，由Z、W生成的白色沉淀均溶解，由Y生成的白色沉淀不溶解。

④在相同条件下，将足量的Y的溶液分别加到相同物质的量浓度、相同体积的Z和W的溶液中，都有气泡出现。其中W溶液中气泡出现较快。

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①Z+石灰水（离子方程式）                                           ；

②X+ CO2（化学方程式）                                             ；

③W（化学方程式）                                            。
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