问题 选择题

下列叙述正确的是(  )

A.25℃时,MgCO3饱和溶液中c(Mg2+)=2.6×10-3mol•L-1,CaCO3饱和溶液中c(Ca2+)=5.3×10-5mol•L-1,向浓度均为0.1 mol•L-1的MgCl2和CaCl2混合溶液中逐滴加入0.1 mol•L-1的Na2CO3溶液,首先生成CaCO3沉淀

B.向硫酸亚铁溶液中加入氯水,再加入KSCN溶液,溶液变为红色,说明硫酸亚铁溶液中存在Fe3+

C.向某溶液中加入盐酸酸化的氯化钡溶液,有白色沉淀生成,该溶液中一定含有SO42-

D.除去Cu粉中混有的CuO,可将混合物加入到稀硝酸中,充分反应后过滤、洗涤

答案

A.25℃时,MgCO3饱和溶液中c(Mg2+)=2.6×10-3mol•L-1,CaCO3饱和溶液中c(Ca2+)=5.3×10-5mol•L-1,则Ksp(MgCO3)=6.76×10-6>Ksp(CaCO3)=2.8×10-9,所以向浓度均为0.1 mol•L-1的MgCl2和CaCl2混合溶液中逐滴加入0.1 mol•L-1的Na2CO3溶液,首先生成CaCO3沉淀,故A正确;

B.因氯水具有氧化性,将亚铁离子氧化为铁离子,则向硫酸亚铁溶液中先加入KSCN溶液,不变色,再加入氯水溶液变为红色,说明硫酸亚铁溶液中存在Fe2+,故B错误;

C.AgCl也是不溶于水、不溶于酸的白色沉淀,则向某溶液中加入盐酸酸化的氯化钡溶液,有白色沉淀生成,该溶液中可能含有Cl-或含有SO42-,但二者不能同时存在,故C错误;

D.因Cu与稀硝酸反应,则除去Cu粉中混有的CuO,可将混合物加入到稀盐酸(或稀硫酸)中,充分反应后过滤、洗涤,故D错误;

故选A.

填空题

阅读短文,用括号中的动词的适当形式填空,使短文意思完整、通顺。

    

     In some science fiction movies, people in the future have their own robots. They are just like humans.

These robots 1______(use) by the people to do the? housework and the most unpleasant jobs. Some

scientists 2______(mink) that there will be such robots in the future. However, they agree it may take

hundreds of years.Now scientists 3______ (try) to make robots look like people and do the same thing as

us. Over the years, Japanese companies 4______(make) robots walk and dance already.

     But scientist James White 5______(disagree). He thinks that it will be difficult for a robot to do the same

thing as a person. Once he gave us an example. It was easy for a child to wake up while he 6______(sleep)

and know where he was, but robots couldn't do this. But other scientists disagree. They think that robots

7______(be) able 10 talk to people in 25 to 50 years. Scientists are not just trying to make robots look like

people. Several years ago, some robots 8______(invent). Those robots looked like huge arms. They did the

simple jobs over and over again. People would not like to do such jobs and would get bored.

     In the future, new robots will have many shapes. Some might even look like snakes. After an earthquake,

a snake robot could help look for people under buildings. That may not seem possible now, but computers

and space rockets 9______(seem) impossible a hundred years ago. We don't know what 10______(happen)

in the future. Let's wait!

单项选择题