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问题 选择题

某CuO粉末与适量的硫酸（ρ=1.7g•cm-3）在微热下充分反应，冷却后恰好全部形成CuSO4•5H2O（设反应过程中无水份损失）．则此硫酸溶液的物质的量浓度为（　　）

A．8.5mol•L-1

B．10.0mol•L-1

C．17.0mol•L-1

D．18.4mol•L-1

答案

CuO粉末与适量的硫酸微热下充分反应，冷却后恰好全部形成CuSO4•5H2O，可以改写呈成CuO•H2SO4•4H2O，故原硫酸溶液中m（H2SO4）：m（H2O）=98：4×18=98：72，故该硫酸的质量分数为

98
98+72
=
98
170
，该硫酸的密度ρ=1.7g•cm-3，故该硫酸的物质的量浓度c=
1000×1.7×
98
170
98
mol/L=10mol/L，

故选B．

单项选择题

It is clear that some chemicals can damage the health of animals and humans. (1) , this is not the only problem that (2) be caused by the careless use of chemicals. Chemicals can also (3) the ecological balance of the environment. If the ecological balance is disturbed, the results can be (4) serious.The (5) of DDT illustrates the problem. DDT, a chemical which kills insects, at first seemed to be a perfect answer (6) many problems. It would control insects that caused dangerous diseases, (7) insects that caused billions of dollars of damage to crops every year. Governments permitted and even (8) the use of DDT. Farmers in many countries (9) to spray it on their crops. The (10) results were good. Damage to crops (11) down, and profits went up. However, the chemical had effects which the scientists didn’t see in (12) . First, it also killed insects which were the (13) enemies of the harmful insects and which were therefore beneficial to farmers. Second, and perhaps worse, DDT did not kill (14) harmful insect. A few insects had natural resistance to the chemical. They (15) and reproduced in large numbers. In a few years there were large numbers of insects which were not (16) by DDT, and there were (17) insects which Could act as natural (18) on these new "super-insects". Finally, it became clear that DDT was not solving the insect problem. In fact, it was making the problem worse. It (19) became necessary to find a second (20) for the effects of the first.

第（1）空应选择（）

A．Therefore

B．However

C．Meanwhile

D．Besides
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判断题

企业为了降低损失，绝对不会在亏损的情况下继续生产。
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