将a mol钠和a mol铝一同投入m g足量水中，所得溶液密度为d g·mL-

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问题选择题

将a mol钠和a mol铝一同投入m g足量水中，所得溶液密度为d g·mL^-1，该溶液的溶质质量分数为（）

A．%

B．%

C．a/2%

D．3a/2%

答案

答案：C

由2Na+2H₂O2NaOH+H₂↑，2Al+2NaOH+2H₂O2NaAlO₂+3H₂↑可知：

2Na — 2NOH — H₂↑

a mol a mol a/2 mol

2Al — 2NaOH — 2NaAlO₂— 3H₂↑

a mol a mol a mol 3a/2 mol

阅读理解

Read and judge. 阅读短文，判断正(T)误(F)。

Tom is a primary school student. He is in Grade Two now. He has a round face and wears glasses. He

likes football and swimming. But today he's not at school. He's ill. He's in bed. He had a bad cold. He must stay

in bed for a week. But that's good news for him, because he doesn't like school!

( ) 1. Tom wears glasses.

( ) 2. Tom doesn't like football.

( ) 3. Tom isn't at school. He's ill.

( ) 4. Tom is ill, so he is very sad.

( ) 5. Tom has a bad cold. He can't go to school.

单项选择题

城市土地利用数量结构指标可与国外大城市横向比较，从发达国家的土地利用结构情况来看，最主要的特征是（）用地的比重较大。

A.建设

B.绿地

C.基础设施和公共设施

D.军事