问题 计算题

根据质量守恒定律,6g镁和8g氧气充分反应,可生成14g氧化镁。这种说法正确吗?为什么?如不正确,请加以改正。

答案

是错误的。在化学反应中,各反应物之间是按照一定的质量比相互作用的。因此,质量守恒定律中“参加化学反应的各物质的质量总和”就不是任意比例的反应物的质量的简单加和,而应是按一定的质量比进行反应的各反应物的质量总和。所以本题简单地用:6g+8g=14g的计算方法就得出生成物氧化镁的质量。

可以用以下方法求出氧化镁的质量:

解:2Mg+O22MgO

2×24 32

 6  8

由于,所以氧气过量。

设6g镁能与氧气反应的质量为x。

2Mg+O22MgO

48 32

6g x

x=4g

生成氧化镁的质量:6g+4g=10g。

所以上述说法可以这样改正:根据质量守恒定律,6g镁和4g氧气恰好完全反应后,可以生成10g氧化镁。

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How can I win a Nobel Prize for writing? Here is the s__小题1:_ from this year’s winner: make it short, keep it real, and work hard.

Canadian author Alice Munro,82,was awarded the 2013 Noble Prize in the literature(文学)。She is k_小题2:__ for her short stories about personal relationship of ordinary people, usually women.

Munro was born in a farmer family in Ontario. The family was very poor. Munro did a lot of physical work a___小题3:__ a young girl.

But she decided to be a writer when she was 12. She turns her hard childhood into great writing i__小题4:__.

The story Dear Life, for example, opens with a description of the neighborhood in which Munro grew up.

Besides, she talked a__小题5:__ her poor relationship with her mother in many of her stories, such as Lives of Girls and Women and Friend of My Youth.

Since she published her f_小题6:_ book in 1968, Munro has won many awards, with the Nobel Prize as her biggest honor. But Munro doesn’t see h____小题7:____ as a talented writer.

“I’m the opposite of a writer with a quick gift. I don’t understand it very easily at all, the “it” being whatever I’m trying to do,” she said.

Do you d___小题8:___ of becoming a writer while thinking you are not that talented? Munro has a tip for you: use notebooks and write a l__小题9:__.

“I have lots of notebooks that contain this terribly clumsy(蹩脚的) writing,” she said .But it helps her arrange her mind. “Stories would just be working in my head for so long that I was deep into t_小题10:_ when I started to write.”

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