问题 填空题

化学与生活、生产、科技发展息息相关。

(1)温泉中含有的钙、镁、钠、硫等矿物质对人体具有保健及美容的作用,这里的“钙、镁、钠、硫”指的是            (填“分子”、“原子”或“元素”)。

(2)硅酸钠(Na2SiO3)可用作黏合剂和防火材料,其中Si元素的化合价为________。

(3)氮气常用于粮食的保护气是因为                                                   

(4)“嫦娥三号”使用的燃料是液氢,助燃剂是液氧,该燃料燃烧的化学方程式为             

(5)汽车是重要的交通工具。

①汽车使用天然气作燃料,排放污染较低。天然气中碳、氢元素的质量比为_____。

②请完成完成铅酸电池充电反应的方程式:

2PbSO4 + 2H2OPb + 2H2SO4 + _______。

答案

(1)元素              (2)+4           (3)氮气化学性质稳定

(4)2H2+O22H2O                  (5)①  3:1               ②PbO2

题目分析:(1)这里的“钙、镁、钠、硫”指的是相应的元素。

(2)在化合物中,各元素化合价的代数和为零。在硅酸钠(Na2SiO3)钠元素显+1价,氧元素显-2价,可计算出硅元素的化合价为+4价。

(3)氮气常用于粮食的保护气是因为氮气化学性质稳定

(4)根据题意可知,反应物为液氢(H2)和液氧(O2),条件为点燃,所以其反应的化学方程式为:2H2+O22H2O

(5)①天然气的化学式为CH4,其中碳、氢元素的质量比为(12╳1):(1╳4)=12:4=3:1②根据“在化学变化前后,原子的个数不发生改变”可推得空格中的物质的化学式。

原子种类反应前原子个数反应后原子个数空格中含有的原子个数
Pb211
S220
O1082
H440
 

所以空格上的化学式为:PbO2

阅读理解

A judge was working in his room one day when a neighbour ran in and said, “If one man's cow kills another's, is the owner of the first cow responsible?”

“It depends,” answered the judge.

“Well,” said the man, your cow has killed mine.

“Oh,” answered the judge. “Everyone knows that a cow cannot think like a man, so a cow is not responsible, and that means that its owner is not responsible either.”

“I am sorry, Judge,” said the man. “I made a mistake. I meant that my cow killed yours.”

The judge thought for a few seconds and then said,“ When I think about it more carefully, this case is not as easy as I thought at first. ”And then he turned to his clerk and said, “Please bring me that big black book from the shelf behind you.”

小题1:The neighbour asked the judge_______.

A.whether the first cow was responsible

B.whether the owner of the first cow was responsible

C.whether both cows were responsible

D.whether both the owners were responsible小题2:When the neighbour reported that the judge's cow had killed his, the judge answered that______.

A.a cow was responsible

B.its owner was not responsible

C.neither a cow nor its owner was responsible

D.his cow was responsible小题3:When the neighbour heard this, he told the judge that_______.

A.there was nothing happened

B.his cow had been killed

C.it was his cow that had killed the judge's

D.both cows had been killed小题4:When the judge heard that his cow had died, he________.

A.got angry

B.said nothing

C.put his neighbor into prison

D.changed what he had said at first小题5:In this story the judge was______.

A.a clever judge

B.a humorist

C.unfair

D.foolish

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