问题 选择题

设nA为阿伏加德罗常数的数值,下列说法正确的是(  )

A.1molNa燃烧生成Na2O2失去的电子数为2nA

B.常温常压下,32gO3含有原子数为2nA(相对原子质量:O16)

C.常温常压下,22.4LCO2含有CO2分子数为nA

D.1L0.5mol•L-1的(NH42SO4溶液中含NH4+数为nA

答案

A、1molNa燃烧生成Na2O2,Na~Na+~e-,所以1molNa燃烧生成Na2O2失去的电子数为nA,故A错误;

B、32gO3物质的量=

32g
48g/mol
=
2
3
mol,1molO3分子中含有3mol氧原子,所以
2
3
molO3分子中含氧原子数2mol即2nA,故B正确;

C、常温常压下,22.4LCO2物质的量不一定是1mol,所以含有CO2分子数不一定为nA,故C错误;

D、1L0.5mol•L-1的(NH42SO4溶液中铵根离子应为1mol,但水溶液中铵根离子水解,所以物质的量小于1mol,故D错误;

故选B.

阅读理解

阅读理解。

     Ben Jones was walking home from school one day when he saw a black cat. It was walking across the

srteet in front of him.Ben stopped, turned around, and walked down a different srteet to go home. Why did he

do that?

     "It's unluchy when a black cat crosses the street in front of you," says Ben, "I did not want to walk down

that street!"

     Many people think that some things bring bad luch of good luck. For example, some people think that 13

is an unlucky number. They never invite 13 people to a party.

     "I never walk under a ladder (梯子)," says Ben. "And I never open an umbrella inside the house. They both

bring bad luck."

     And what brings good luck? "We have a horseshoe over the front door of our house for good luck," says

Ben.  

     "And when I find a peney on the ground, I always pick it up. That brings me good luck all day!"

1. Why did Ben turn aroundd when he saw the black cat crossing the street?

A. Because he thought it was unlucky.

B. Because he disliked a black cat.

C. Because he was afraid of the cat.

2. In western countries,which number do some people think is unlucky?

A.  4.

B. 10.

C. 13.

3. Which of the following things can bring people good luck?

A. Opening an umbrella inside the house.

B. Walking under a ladder.

C. Picking up a penny on the ground.

4. Where does Ben's family have a horseshoe?

A. Over the front door.

B. Inside the house.

C. Under a ladder.

5. Which is the best title of the passage?

A. A black cat.

B. Good luck and bad luck.

C. Good things can bring good luck.

填空题