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在50 mL a mol·L－1的硝酸溶液中，加入6.4 g Cu，全部溶解，假设硝酸的还原产物只有NO2和NO，将反应后溶液用蒸馏水稀释至100 mL时测得c(NO3-)＝3 mol·L－1。

（1）稀释后的溶液pH＝          ；

（2）若a＝9，则生成的气体中NO2的物质的量为         mol。

答案

（1）0           （2）0.125　

题目分析：（1）因为铜全部溶解，因此溶液中铜离子的物质的量为0.1 mol，那么与铜离子相结合的硝酸根离子的物质的量为0.2 mol。又因为溶液中总的硝酸根离子的物质的量为0.3 mol，所以以硝酸形式存在的离子的物质的量为0.1 mol，也可以理解为溶液中剩余硝酸的物质的量为0.1 mol，那么硝酸的浓度为1mol·L－1，所以其pH＝0。（2）若a＝9，则题中所提供的硝酸总的物质的量为0.45 mol，减去剩余的0.3mol，那么被还原的硝酸的物质的量为0.15 mol。因为这是一个氧化还原反应，氧化剂所得到的电子与还原剂所失去的电子的物质的量相等，还原剂铜所失去的电子一定为0.2mol，假设反应中生成的二氧化氮的物质的量为x mol， 那么一氧化氮的物质的量就为：（0.15－x）mol，如是有如下关系：

0.2=（0.15－x）×3＋x，解之得：x="0.125" mol

单项选择题

对病毒基因组转录的调控起作用的长末端重复序列

A．HIV的env基因
B．HIV的poi基因
C．HIV的gag基因
D．HIV的LTR基因
E．HIV的tat基因

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单项选择题

Electronic mail has become an extremely important and popular means of communication.
The convenience and efficiency of electronic mail are threatened by the extremely rapid growth in the volume of unsolicited commercial electronic mail. Unsolicited commercial electronic mail is currently estimated to account for over half of all electronic mail traffic, up from an estimated 7 percent in 2001, and the volume continues to rise. Most of these messages are fraudulent or deceptive in one or more respects.
The receipt of unsolicited commercial electronic mail may result in costs to recipients who cannot refuse to accept such mail and who incur costs for the storage of such mail, or for the time spent accessing, reviewing, and discarding such mail, or for both. The receipt of a large number of unwanted messages also decreases the convenience of electronic mail and creates a risk that wanted electronic mail messages, both commercial and noncommercial, will be lost, overlooked, or discarded amidst the larger volume of unwanted messages, thus reducing the reliability and usefulness of electronic mail to the recipient. Some commercial electronic mail contains material that many recipients may consider vulgar or pornographic in nature.
The growth in unsolicited commercial electronic mail imposes significant monetary costs on providers of Internet access services, businesses, and educational and nonprofit institutions that carry and receive such mail, as there is a finite volume of mail that such providers, businesses, and institutions can handle without further investment in infrastructure. Many senders of unsolicited commercial electronic mail purposefully disguise the source of such mail.
Many senders of unsolicited commercial electronic mail purposefully include misleading information in the messages’ subject lines in order to induce the recipients to view the messages. While some senders of commercial electronic mail messages provide simple and reliable ways for recipients to reject (or ’opt-out’ o0 receipt of commercial electronic mail from such senders in the future, other senders provide no such ’opt-out’ mechanism, or refuse to honor the requests of recipients not to receive electronic mail from such senders in the future, or both.
Many senders of bulk unsolicited commercial electronic mail use computer programs to gather large numbers of electronic mail addresses on an automated basis from Internet websites or online services where users must post their addresses in order to make full use of the website or service.
The problems associated with the rapid growth and abuse of unsolicited commercial electronic mail cannot be solved by the government alone. The development and adoption of technological approaches and the pursuit of cooperative efforts with other countries will be necessary as well.

It can be inferred from Paragraph 6 that bulk unsolicited commercial e-mail will probably spread ______.

A．harmful virus

B．unpleasant news

C．advertisements

D．adult jokes
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