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问题 问答题

一定质量的锌粒与某稀硫酸恰好反应，生成0.4克氢气，同时得到112.4克溶液，求：

（1）锌粒的质量．               

（2）稀硫酸的溶质质量分数．

答案

设锌粒的质量是Xg，纯硫酸的质量是Yg．

Zn+H2SO4═ZnSO4+H2↑

65   98         2

X    Y        0.4

65
2
═
X
04

X=13

98
2
═
Y
04

Y=19.6

∵原硫酸溶液的质量等于112.4+0.4-13=99.8g．

∴稀硫酸的溶质的质量分数等于

19.6
99.8
×100%═19.7%．

答：锌粒的质量是13g，稀硫酸的溶质的质量分数为19.7%．

单项选择题

In the past ten years, there have been several improvements in mountain-climbing equipment. These improvements have made the sport both safer and more enjoyable for experienced climbers. Despite these improvements, however, the rate of mountain-climbing injuries has doubled in the past ten years.
If all of the statements above are true, which of the following, if true, best reconciles their apparent discrepancy ？（）

A．Many climbers, lulled into a false sense of security, use the new equipment to attempt climbing feats of which they are not capable.

B．Some mountain-climbing injuries are caused by unforeseeable weather conditions.

C．Mountain climbing, although a dangerous sport, does not normally result in injury to the experienced climber.

D．In the past ten years there have been improvements in mountain-climbing techniques as well as in mountain-climbing equipment.

E．Although the rate of mountain-climbing injuries has increased, the rate of mountain-climbing deaths has not changed.
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问答题 简答题

标准地名地址的管理分为哪两个阶段进行？
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