设氯原子的质量为ag，12C原子的质量为bg，用NA表示阿伏加德罗常

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问题选择题

设氯原子的质量为ag，¹²C原子的质量为bg，用N_A表示阿伏加德罗常数的值，则下列说法正确的是

A．氯元素的相对原子质量为12/b

B．mg该氯原子的物质的量为m / N_A mol

C．该氯原子的摩尔质量是a N_A

D．ng该氯原子所含的电子数是17n/a

答案

根据相对原子质量的定义，氯元素的相对原子质量="ag/(bg/12)=" 12a/b,AC错；

mg该氯原子的物质的量=mg/(12a/b)g.mol^-1==mb/12amol,B错；

完形填空

从方框中选择正确的选项补全对话：

Tom: ___1______ , do you know?

Jim: James Naismith. Am I right?

Tom: That’s right! _____2_____

Jim: Was he from the U.S.A.?

Tom: No, he was a Canadian.

Jim: ____3_____

Tom: He invented it in 1891.

Jim: Wow, that was a long time ago!______4______

Tom: He just hoped the students could play it indoors and even in bad weather.

Jim: ______5_____. Can you tell me?

Tom: Well, just put the ball into the other side’s basket.

Jim: That’s easy. Let’s play basketball together.

Tom: OK, let’s go.

选择题

The problem is so difficult that ______ students can work it out. [ ]

A. a few

B. a little

C. few

D. little