问题 多选题

在天平两边的托盘上,各放一个烧杯,调节天平至平衡.向左边烧杯中注入100克9.8%的稀硫酸,右边烧杯中注入100克7.3%的稀盐酸,再向左边烧杯中加入a克铝粉,右边烧杯中加入b克镁粉,充分反应后,最终天平仍平衡,则a与b的关系理的是(  )

A.a=b≥2.4克

B.a=b≥1.8克

C.若a=1.65克,则b=1.6克

D.若a=1.8克,则b=2.4克

答案

第一种情况:根据金属过剩,按酸反应完全计算,加入金属质量应符合以下要求:

2Al+3H2SO4═Al2(SO43+3H2

2×273×986

1.8g 100g×9.8%0.2g

Mg+2HCl═MgCl2+H2

24 732

2.4g 100g×7.3%0.2g

100g 9.8%的硫酸至少需要1.8g铝粉参加反应,才能生成0.2g H2

要产生0.2H2,至少需要2.4g镁参加反应,考虑天平平衡a=b≥2.4g,所以A正确.

第二种情况:酸过剩,金属反应完全,要使天平平衡,必须满足两烧杯中加入金属质量减去逸出H2的质量差相等,则:

2Al+3H2SO4═Al2(SO43+3H2

2×276

ag

6a
2×27
g

Mg+2HCl═MgCl2+H2

24 2

bg

2
24
bg

天平平衡必须满足a-

6a
2×27
g=b-
2
24
bg

a
b
=
1.65
1.6

所以C符合要求

故选A、C

阅读理解

阅读理解。

     Steven Jobs, the designer (设计者) of Apple Computer, was not clever when he was in school.

At that time, he was not a good student and he always made troubles with his schoolmates. When he

went into college, he didn't change a lot. Then he dropped out (退学).But he was full of new ideas.

After he left college, Steven Jobs worked as a video game designer. He worked there for only several

months and then he went to India. He hoped that the trip would give him some new ideas and give him

a change in life.   Steven Jobs lived on a farm in California for a year after he returned from India. In 1975, he began to make a new type of computer. He designed the Apple Computer with his friend in his garage (汽车库). He chose the name "Apple" just because it could help him to remember a happy summer he

once spent in an apple tree garden. His Apple Computer was such a great success that Steven Jobs

soon became famous all over the world.

1. Steven Jobs was not a good school because he _____.

A. never did his lessons

B. was full of new ideas

C. always made troubles with

D. dropped out

2. Steven Jobs didn't finish college, did he? _____.

A. Yes, he did

B. No, he didn't

C. Yes, he didn't

D. No, he did

3. Steven Jobs designed his new computer _____.

A. in India

B. with his friend

C. in an apple tree garden

D. by himself

4. Steven Jobs was famous' for his _____ all over the world.

A. new idea

B. apple

C. Apple Computer

D. video games

5. From this passage we know _____.

A. Steven Jobs didn't finish his studies in the college because he hated his schoolmates

B. Steven Jobs liked travelling in India and California

C. Steven Jobs liked trying new things and making his new ideas become true

D. Steven Jobs could only design video games

单项选择题