20g含杂质（杂质不溶于水，也不溶于酸）的锌样品，与一定质量的_爱下问搜题

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问题计算题

20g含杂质（杂质不溶于水，也不溶于酸）的锌样品，与一定质量的稀硫酸恰好完全反应，所得溶液质量为80.5g，同时生成氢气0.4g。试计算：

（1）样品中锌的质量分数；

（2）完全反应后生成溶液中溶质的质量分数；

（3）所用稀硫酸的质量分数 (计算结果保留到0.01%)。

答案

（1）65% (2)40% (3)28.9%

解，设样品中锌的质量为x，反应后生成硫酸锌的质量为y，所用稀硫酸溶质质量为z，根据题意，得

Zn + H₂SO₄="=" ZnSO₄+ H₂↑

65 98 161 2

x z y 0.4g

（1）65：2=x：0.4g 解得 x=13g

（2）161：2=y：0.4g 解得 y=32.2g

（3）98：2 = z：0.4g 解得 z=19.6g

填空题

管道的热补偿包括（）和（）补偿。

单项选择题

Melissa and Love Letter made use of the trust that exists between friends or colleagues. Imagine receiving an (66) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (67) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’ s address book ,previous emails, web pages (68) .
As administrators seek to block dangerous email attachments through the recognition of well- known (69) , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to . bat and . cnd plus a whole list of other extensions and will still run and successfully infect target users. Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which, while displaying some cute animation, simultaneously runs commands in the background to steal your passwords and give the (70) access to your network.

A．virtual

B．virus

C．worms

D．bacteria