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问题 填空题

某同学设计了如下实验，以测定CaCO3、(NH4)2CO3和NH4Cl固体混合物中氮元素的质量分数。实验过程如下图所示：

请回答:

（1）为进行操作①、②，需要用到的玻璃仪器有_____________________。

（2）原样品中氮元素的质量分数为_________________（用含W、m的代数式表示）。

（3）若该同学由于操作不当而使测定结果偏低，其原因可能是_________（填字母）。

a. 试剂①用量不足               b. 固体未经洗涤

c. 试剂②用量不足                d. 气体C未经干燥

答案

（1）烧杯、漏斗、玻璃棒（共3分）（2）（1分）  

（3）a、b、c （共3分）

单项选择题 共用题干题

患者女，67岁，全牙列缺失，全口义齿修复。

对无牙颌的上颌后堤区叙述正确的是（）。

A.位于前颤动线

B.位于后颤动线

C.位于前后颤动线之间

D.位于腭小凹前6mm

E.位于腭小凹前4mm
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单项选择题

A recent spate of art thefts at a major museum has led to a drastic increase in the insurance premiums that the museum must pay to insure its collection. Many art fans are concerned that the museum, which traditionally has charged no entrance fee, will be forced to charge a high entrance fee in order to pay for the increased insurance premiums.
Which of the following, if true, would most alleviate the concern of the art fans that the museum will be forced to charge high entrance fees ？（）

A. Law enforcement officials recently apprehended the Belgian Bobcat, a notorious art thief who has been linked to at least 20 art heists.

B. Citing a dispute with the insurance company over the terms of its coverage, the museum has chosen to cancel its insurance policy.

C. The majority of visitors to the museum are schoolchildren, who could not reasonably be expected to pay a high entrance fee.

D. The museum pays for the majority of its total expenses from its large endowment, which is earmarked specifically for purchasing new art.

E. The museum recently installed a state-of- the-art burglar alarm system that will make future thefts almost impossible.
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