问题 选择题

一定温度下,将一定质量的冰醋酸加水稀释过程中,溶液的导电能力变化如右图所示,下列说法正确的是

A.a、b、c三点溶液的pH:a>b>c

B.若用湿润的pH试纸测试c处溶液的pH,比实际的pH偏小

C.a、b、c三点溶液用1 mol/L的NaOH溶液中和,消耗NaOH溶液的体积a>b>c

D.若在O点醋酸双聚成八元环。则其结构式为:

答案

答案:D

根据溶液的导电能力可知,氢离子浓度由大到小的顺序是bac,所以pH由大到小的顺序是cab,A不正确;pH试纸如果事先润湿,则相当于稀释醋酸,氢离子浓度降低,pH增大,B不正确;醋酸在稀释过程中,醋酸的物质的量是不变的,中和氢氧化钠的能力是不变的,C不正确;由于氧元素的非金属性强,能形成氢键,所以选项D正确,答案选D。

单项选择题

I was a single parent of four small children, working at a low paid job. Money was always tight, but we had a (1) over our heads, food on the table, clothes on our backs, and if not a lot, always (2) . Not knowing we were poor, my kids just thought I was (3) . I’ve always been glad about that.

It was Christmas time, and although there wasn’t (4) for a lot of gifts, we planned to celebrate with a family party. But the big (5) for the kids was the fun of Christmas (6) .

They planned weeks ahead of time, asking (7) what they wanted for Christmas. Fortunately, I had saved MYM120 for (8) to share by all five of us.

The big (9) arrived. I gave each kid a twenty-dollar bill and (10) them to look for gifts of about four dollars each. Then everyone scattered. We had two hours to shop; then we would (11) back at the "Santa’s Workshop"

Driving home, everyone was in high Christmas spirits, (12) my younger daughter, Ginger, who was unusually (13) She had only one small, flat bag with a few candies—fiftycent candies I was so angry, but I didn’t say anything (14) we got home. I called her into my bedroom and closed the door, (15) to be angry again. This is what she told me.

"I was looking (16) thinking of what to buy, and I (17) to read the little cards on the ’Giving Trees’. One was for a little girl, four years old, and all she (18) for Christmas was a doll. So I took the card off the tree and (19) the doll for her. We have so much and she doesn’t have anything. "

I never felt so (20) as I did that day.

1()。

A.forgot 

B.stopped 

C.failed 

D.hated

问答题 简答题