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问题 计算题

黄铜是一种重要的金属材料，是铜和锌的合金。为了测定某黄铜样品中铜的质量分数，取10g该黄铜样品粉末加入到25g的稀硫酸中，恰好完全反应，测得产生氢气0.1g。试求：

（1）该黄铜样品中铜的质量分数。  （2）所用稀硫酸中溶质的质量分数。

答案

（1）67.5%      （2）19.6%

           

题目分析:黄铜是铜和锌的合金, 加入到稀硫酸中,由于铜的活动性比H弱,所以它不会和稀硫酸反应,生成的氢气应该是锌和稀硫酸反应得到的,故可根据Zn+H2SO4=ZnSO4+H2↑中氢气质量求出锌的质量,即可求出黄铜样品中铜的质量分数了,同时,锌是和稀硫酸中的溶质发生反应,同样可以通过Zn+H2SO4=ZnSO4+H2↑求出稀硫酸中溶质的质量,稀硫酸溶液的质量又是已知的,根据溶质质量分数=溶质质量/溶液质量×100%即可算出

解:设黄铜中锌的质量为x,稀硫酸中的溶质质量为y

Zn+H2SO4=ZnSO4+H2↑

65   98         2

x    y         0.1g

65:2=X：0.1g

X=3.25g

98:2=Y：0.1g

Y=4.9g

∴（1）黄铜样品中铜的质量为：10g–3.25g=6.75g

∴黄铜样品中铜的质量分数为：6.75g/1.g╳100%=67.5%

（2）稀硫酸中溶质的质量分数为：4.9g/25g╳100%=19.6%

阅读理解

第四部分阅读理解（共15个小题，每小题1分，满分15分）

In the western part of the United States where the Indians lived, a little mouse called the “bean mouse” became a guide to rich stores of good and tasty difficult-to-find food. Each season, the little animal would work very hard to search out the rare beans, and “cache” them away in its nest (窝). The Indians learned of this and found out the hiding place. They collected most of the beans for themselves. When the mouse returned to its home and found only a few of the tasty beans left, it set to work, harder than ever before, gathering more beans. This was a fine thing for the Indians, who had only to look for the nest, while the mouse had to look for the beans. But the Indians returned the favour (恩惠，善意) by always making sure that the animal had enough for the winter.

61. The Indians valued the bean mouse _________.

A. as a guide to food                                     B. as fertile (肥沃的) land

C. because it made a good pet                              D. because its fur was valuable

62. The underlined word “cache” means _______.

A. throw them in every place                      B. place them in a hiding place for later use

C. put them in its home                                 D. lay them under the mud

63. The passage says that the bean mouse was ________.

A. fearless               B. friendly                    C. rare                     D. hard-working

64. The Indians are shown to be ________.

A. clever                 B. hard-working        C. unkind                D. educated

65. The best title for this passage is _________.

A. Man’s Best Friend                                   B. Habits of the Bean Mouse

C. A Search of Rare Beans                              D. The Indians and the Mouse
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单项选择题 A1型题

血钙中直接发挥生理作用的物质为（）

A.草酸钙

B.血浆蛋白结合钙

C.磷酸氢钙

D.氯离子

E.钙离子
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