问题 选择题

下列实验操作错误的是

A.蒸馏时,应使温度计水银球靠近蒸馏烧瓶支管口

B.分液时,分液漏斗中下层液体从下口放出,上层液体从上口倒出

C.浓H2SO4稀释时,应将浓H2SO4慢慢加到H2O中,并及时搅拌和冷却

D.用酒精萃取碘水中的碘

答案

答案:D

酒精和水是互溶的,因此不能用作萃取碘水中碘的萃取剂,应该用苯或四氯化碳,选项D不正确,其余都是正确的,答案选D。

填空题
阅读理解

Drinking a lot of water does not do any good to the body, according to two experts in the United States. In fact, they warn, drinking too much water could be, in certain Cases, harmful.

In a study, Dr Stanly Goldfarb and Dr Dan Negoianu, both of the Renal, Electrolyte and Hypertension Division at the University of Pennsylvania, the United States, have denied the popular belief that drinking a lot of water clears body toxins (毒素) better, improves skin, and helps reduce weight.

Dr Goldfarb and Dr Negoianu say that they found little proof to support the public opinion that drinking 8 glasses of water every day benefits health. At the same time, they found little proof of harm in drinking 8 glasses of water every day.

It is widely believed that in some cases — such as athletes, people who live in hot, dry  environments, and those with certain medical conditions — drinking a lot of water indeed helps,  but no studies have been done to prove the benefits of this practice in average, healthy people, the  website medheadlines. com reports.

The study at the University of Pennsylvania also examined reports that some people experienced increased headaches when their consumption of water was low. In one small study, which the doctors reviewed, the group drinking the most water reported fewer headaches than the control group, “but the difference in the number of headaches was so small between the two groups as to be considered unimportant.”

The researchers concluded that there is no scientific proof to support that average, healthy people need to drink at least 8 glasses of water each day.

The website medheadlines. com says that, according to an Indian doctor, drinking too much water is harmful. If water enters the body more quickly than it can be removed, problems can occur.

1. What’s the key message delivered in the passage?

A. Drinking too much water might bring harm.

B. Whether to drink enough water makes no difference.

C. Drinking too much water may cause headaches.

D. Average, healthy people should drink more water.

2. We can learn from the passage that 8 glasses of water every day ________.

A. proves good for the body             B. has scientific proof of harm

C. is sure to reduce headaches            D. is generally considered necessary

3. Who may agree that drinking lots of water helps to lose weight?

A. Two experts.                     B. General public.

C. An Indian doctor.                  D. A website.

4. According to the passage, we know that ________.

A. the website medheadlines. com is developed by an Indian doctor

B. the study was carried out by two experts with an Indian doctor

C. the two experts performed the study at the University of Pennsylvania

D. drinking 8 glasses of water every day can cure certain diseases