问题 选择题

用NA表示阿伏加德罗常数的值.下列叙述正确的是(  )

A.1 mol的碳烯(:CH2)含电子数为6 NA

B.一定温度下,15 g甲醛和乙酸的混合物含O原子数为0.5 NA

C.常温常压下,4.6 g乙醇中含有C-H键的个数为0.6 NA

D.标准状况下,11.2 L庚烷完全燃烧后生成的CO2分子数为3.5 NA

答案

A、1个碳烯中含有8个电子,所以1mol的碳烯(:CH2)含电子数为8NA,故A错误;

B、15g甲醛的物质的量为0.5mol,1个甲醛含有的O原子数分别为1,所以15g甲醛中含有的O原子数分别为0.5NA,15g乙酸的物质的量0.25mol,1个乙酸含有的O原子数分别为2,所以15g乙酸中含有的O原子数分别为0.5NA,所以15g甲醛和乙酸的混合物含O原子数为0.5 NA,故B正确;

C、4.6g乙醇的物质的量为0.1mol,1个乙醇中含有5个C-H键,所以4.6g乙醇中含有C-H键的个数为0.5NA,故C错误;

D、庚烷是液体,无法计算,故D错误.

故选:B.

多项选择题
写作题

阅读下面的短文,然后按照要求写一篇150词左右的英语短文.

A little boy is telling his Grandma how "everything" is going wrong. School, family

problems, severe health problems, etc.

Meanwhile, Grandma is baking a cake. She asks her grandson if he would like a cake, which,

of course, he does.

"Here, have some cooking oil."

"Terrible!" says the boy.

"How about a couple raw eggs?"

"Terrible! Grandma!"

"Would you like some flour then? Or maybe baking soda?"

"Grandma, those are all awful!"

To which Grandma replies: "Yes, all those things seem bad by themselves, but when they are

put together in the right way, they make a wonderfully delicious cake!

"Life works the same way. Many times we wonder why it would let us go through such bad

and difficult times. But life knows that when it puts these things all in its order, they always work for

good!

"The trials(考验)of life serve a meaningful purpose in making us stronger. Do not lose

heart if life is not easy for you right now, but encourage yourself and know you will be much stronger

mentally and physically because of the trials of life. "

[写作内容]

1.以约30个词概括这段短文的内容;

2.然后以约120个词以"Facing the Trials of Life"为题进行议论,内容包括:

    (1) 你阅读短文后的感受;

    (2) 简述你经历过的一次困难或考验;

    (3) 你认为应当如何看待生活中的考验。

[写作要求]

1.在作文中可以使用自己亲身的经历或虚构的故事,也可以参照阅读材料的内容但不得直接引用原文中的句子;

2.作文中不能出现真实姓名和学校名称。

[评分标准] 概括准确,语言规范,内容合适,篇章连贯。