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问题 选择题

能正确表示下列反应的离子方程式是 (　　)。

A．用铜做电极电解CuSO4溶液：2Cu2＋＋2H2O2Cu＋O2↑＋4H＋

B．钠与CuSO4溶液反应：2Na＋Cu2＋=Cu↓＋2Na＋

C．明矾溶于水产生Al(OH)3胶体：Al3＋＋3H2O=Al(OH)3↓＋3H＋

D．向FeCl3溶液中加入Mg(OH)2：3Mg(OH)2＋2Fe3＋=2Fe(OH)3＋3Mg2＋

答案

答案：D

用铜做电极电解CuSO4溶液，阳极Cu－2e－=Cu2＋，阴极Cu2＋＋2e－=Cu，A错；钠与CuSO4溶液反应，Na先与水反应，生成的NaOH再与硫酸铜反应，B错；铝离子水解不能进行到底，中间用可逆符号，生成的是Al(OH)3胶体，不写沉淀符号，C错。

单项选择题

Why is （） fun？What de lights may its practitioner expect as his reward？First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design. Second is the pleasure of making things that are useful to other people. Third is the fascination of fashioning complex puzzle-like objects of interlocking moving parts and watching them work in subtle cycles, playing out the consequences of principles built in from the beginning. Fourth is the joy of always learning, which springs from the （） nature of the task. In one way or another the problem is ever new, and its solver learns something: sometimes （）, sometimes theoretical, and sometimes both. Finally, there is the delight of working in such a tractable medium. The （）, like the poet, works only slightly removed from pure thought-stuff. Few media of creation are so flexible, so easy to polish and rework, so readily capable of realizing grand conceptual structures.

Yet the program （）, unlike the poet’s words, is real in the sense that it moves and works, producing visible outputs separate from the construct itself. It prints results, draws pictures, produces sounds, moves arms. Programming then is fun because it gratifies creative longings built deep within us and delights sensibilities we have in common with all men.

Yet the program （）, unlike the poet’s words, is real in the sense that it moves and works, producing visible outputs separate from the construct itself.

A．construct

B．code

C．size

D．scale
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问答题 简答题

常见网络互联设备有哪几种。
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