问题 选择题

物质的量浓度相同的下列溶液中,NH+浓度最大的是

A.NH4Cl

B.NH4HCO3

C.CH3COONH4

D.NH4HSO4

答案

答案:D

题目分析:由于NH4++2H2O=NH3·H2O+H3O+,可知,A选项,既不促进也不抑制水解。B选项,HCO3 -水解大于电离,故产生大量氢氧根,促进水解,铵根浓度降低。C选项,CH3COO-水解,产生大量氢氧根,促进铵根水解,铵根浓度降低。D选项,硫酸氢根完全电离,产生大量氢离子,抑制水解。故D选项中铵根离子浓度最大。

阅读理解

阅读理解。

     Whatever our differences as human beings are we all think we're more like the rest of the animal world

than we realize. It is said that we share 40 percent of our genetic (遗传的) structure with the simple worm.

     But that fact has helped Sir John Sulston win the 2002 Nobel Prize for Medicine. Sir John is the founder

of the Sanger Institute in Cambridge, which was set up in 1992 to get further understanding of the human

genome (染色体组).

     To help them do this, they turned to the worm. The nematode (线虫类的) worm is one of the earliest

creatures on planet earth. It is less than one millimeter long, completely transparent and spends its entire life

digging holes through sand. But it still has lots to say about human life, and what can be done to make it

better.

     What the worm told Sir John and his colleagues was that each of the cells in the human body is

programmed like a computer. They grow, develop and die according to a set of instructions that are coded

in our genetic make-up.

     Many of the diseases that humans suffer from happen when these instructions go wrong or are not

obeyed. When the cell refuses to die but carries on growing instead, this leads to cancer. Heart attacks and

diseases like AIDS cause more cell deaths than normal, increasing the damage they do to the body. Sir John

was the first scientist to prove the existence of programmed cell death.

1. Sir John Sulston got a Nobel Prize for Medicine because he has _____ .

A. found that human beings are similar to the worm

B. got the fact we share 40 percent of our genetic structure with the simple worm

C. found the computer which controls each of the cells in the human body

D. proved that cell death is programmed

2. People might be seriously ill if the cells in their body _____.

A. grow without being instructed

B. die regularly

C. fail to follow people's instructions

D. develop in the human body

3. The underlined word " they" in Paragraph 5 refers to _____.

A. cell deaths

B. diseases

C. instructions

D. cells

4. What is the subject discussed in the text?

A. The theory of programmed cell deaths.

B. A great scientist-Sir John Sulston.

C. The programmed human life.

D. Dangerous diseases.

单项选择题