题目
由NaHS、MgSO4、NaHSO3组成的混合物中，已知S元素的质量分数w（S）=a%，则O元素的质量分数w（O）为（ ） A．1.75a% B．1﹣1.75a% C．1.25a% D．无法计算 答案：【考点】混合物中某元素的质量计算． 【专题】化学式的计算；等量代换法． 【分析】NaHS、MgSO4、NaHSO3这几种物质仔细观察有一点规律：（NaH S）、（Mg SO4）、（NaH SO3），可以发现NaH相对原子质量和为24，可以看成与Mg是等同的； 也就是说可以把NaH它们看成一个整体，就可以通过硫的质量分数求出其33、Mr North is now old and very forgetful. One summer
day, he decided to 1 his grandchildren to a
seaside town for a holiday. The town was about a three hours train ride 2
. In order to make the holiday more 3 for
his grandchildren, he kept the name of the town a 4 . But
when they arrived at the station, the door man had forgotten the 5
of the town himself. 6 a friend of 7 was
at the station at that time. He helped to take care of the 8 while
Mr North went back home to find out 9 he was
going.
Mr North was 10
to see Mr North again so soon. But she wins pleased when she
understood 11 he come back. She wrote the name
of the 12 on a piece of paper and sent her
hushed off. Then some 13 later, she was greatly
surprised to see Mr North outside 14 . What was the matter now? Mr
North had forgotten 15 he had left the children.
1. A.
take B. give
C. have D. make
2. A.
farther B. away C.
over D. off
3. A.
interested B. careful C.
interesting D. excited
4. A.
report B. present C.
lesson D. secret
5. A.
people B. road C.
way D. name
6. A.
Luckily B. Surely C.
Finally D. Usually
7. A.
his B.
him C.
himself D. wife
8. A.
Tickets B. children C.
train D. name
9. A. when
B. where C.
how D. whether
10. A.
happy B. angry C.
surprised D. sorry
11. A.
as B. because
C. why D. how
12. A.
friend B. town C.
station D. children
13. A.
months B. weeks C.
minutes D. days
14. A.
soon B. more
C. again D. too
15. A.
who B. where
C. when D. whether
评卷人
得分
五、阅读理解
（每空？ 分，共？
分）
化学 试题推荐
最近更新
