问题 问答题

有一氯化铵样品,可能混有硝酸铵或硫酸铵中的一种,分析其N含量为24.00%。设计一个测定氯化铵的分析方法,配置相应的仪器和药品,判断混入杂质为何物质,并计算氯化铵的含量。

答案

参考答案:分析方法:当氯化铵和硫酸铵混合(无其他杂质)时,可用测定氯离子的方法测定氯化铵含量。但银量法测定氯含量时,大量铵离子的存在对测定有影响,因此,在样品溶解后,应加入过量的NaOH,加热煮沸,驱尽铵离子后,以硝酸中和,并调至所需酸度,然后用银量法测定。
仪器:电子天平、烧杯、电炉、棕色滴定管、锥形瓶等。
药品:硝酸银标准溶液(0.100mol/L)、NaOH、硝酸、铬酸钾指示剂等。
通过计算发现混入的杂质为硫酸铵。样品中氯化铵的含量为56.02%。

填空题
单项选择题

A variety of illegal acts committed by people in the course of their employment, for their own personal gain, are collectively known as white-collar crime. Embezzlement, theft and trading securities (1) insider information are common forms of white-collar crime. The majority of cases involve low-level employees who steal because they are under (2) financial stress. Many plan to (3) the money back as soon as possible but may never do so. Their crimes are usually never (4) because the amounts of money are small, and no one notices the (5) .

(6) , there are some very large cases of white-collar crime, such as multimillion-dollar stock market or banking seams that take years to discover and are extremely difficult and expensive to (7) .

White-collar crime is not (8) to the business sector. Government employment, especially (9) the city level, also provides opportunities to (10) one’s pockets. (11) , building inspectors accept bribes and full-time employees receive (12) payments.

Although white-collar crime is less (13) than street crime, it involves (14) more money and harm to the public than crimes committed by street criminals. It is (15) that there are more criminals (16) the office suites than in the streets, yet the (17) of white-collar makes it difficult to uncover the offenses and pursue the offenders. As the economy (18) from manufacturing to services and electronic commerce, opportunities for white-collar crime (19) , while the technology needed to stop such crimes will (20) .

14()

A.no

B.little

C.far

D.further