试题与答案

250C时,重水(D2O)的离子积为1.6×10-15也可用pH值一样的定义来规

题型:选择题

题目:

250C时,重水(D2O)的离子积为1.6×10-15也可用pH值一样的定义来规定其酸碱度:pD=-lgc(D+),下列叙述正确的是[ ]

①中性D2O的pD=7

②在1LD2O中,溶解0.01molDCl,其pD值为1

③1L0.1mol/L的NaOD的重水溶液,pD=12

④在100mL0 .25rnoL/LDCl的重水溶液中,加入50mL0. 2mol/L NaOD的重水溶液,反应后溶液的pD=1

⑤温度升高,CD+×COD-的值会升高

A.②③

B.③④

C.①②

D.④⑤

答案:

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参考答案:A

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      Many parents are worried that it is dangerous to start serious training in a sport at an early age. Some

doctors agree that young muscles may be damaged by training before they are properly developed. Professional

(专业的) trainers, however, believe that it is only by training young that you can reach the top as a successful

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prepared for failure even after many years of training.

1. This article is most probably taken from ____. [ ]

A. a letter

B. an advertisement

C. a personal diary

D. a newspaper article

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A. feel uncertain if they should let their children train to be sports men or women.

B. try to get financial(财政的) support from the government for their children's training.

C. have to get medical advice from doctors about training methods.

D. prefer their children to be trained as young as possible.

3. Which of the following statements is NOT true? [ ]

A. By starting young, you won't have much time for your schoolwork.

B. Early training may damage your muscles.

C. Most children may become professional sports men after a long period of training.

D. It's very expensive for parents to support their child's development in sports.

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A. to repeat the activities some other day

B. to become less important

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D. to happen again

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A. Most people

B. Some people

C. Hardly any people

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