问题 选择题

小竹同学取少量氧化铜和一定量稀硫酸,经过较长时间加热,氧化铜全部溶解后,立即加入氢氧化钠溶液,结果也没有得到蓝色沉淀,试管中却意外出现了黑色固体.黑色固体是(  )

A.MnO2

B.CuO

C.Cu(OH)2

D.Cu

答案

氧化铜与稀硫酸反应时,应生成硫酸铜和水,硫酸铜溶液在加入氢氧化钠时应有蓝色沉淀,但在加热后,氢氧化铜会分解生成氧化铜和水,由于该溶液经过较长时间的加热温度较高,所以试管内壁会有氢氧化铜分解生成的黑色固体氧化铜生成.

故选B.

填空题
完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项其中有两项为多余选项。

Boys do bad at school

Despite education reforms and more than enough money, more and more boys have been dropping out of high schools in the United Arab Emirates  (阿拉伯联合酋长国 )  for the past few years.  小题1:_They often choose jobs in public services. the army or the police force instead. As a result. only 30% of the universities are made up of male students. Such a condition has also put them at an obvious disadvantage.  小题2:   In such an oil-rich country. families are so wealthy that their children do not need to study hard. Boys often come to school with personal helpers who carry their suitcases for them and help them with their homework. They rely on them to do everything they would otherwise have to do themselves_小题3:_

Public schools usually get enough money from the government.   小题4:  The rest go to private schools where teachers are more interested in pushing children towards a higher education. In public schools. motivation is low and students seem uninterested in learning. Experts agree that teacher training throughout the Emirates needs to be improved.

 小题5:  0ne of them is the population's widespread thinking that the government will always supply young citizens with jobs. Authorities are convinced that just pouring money into the school system won't achieve the desired results. Their aim is to have more Emirati males finish high school and continue to go to university, where they will get degrees and have a bright future.

A. But what comes after oil runs out in the country?.

B. Boys and girls are often separated in public schools.

C. Few women will marry a man with lower education.

D. However. only 40% of all children attend these schools.E.  The Emirati people have been living on the land for centuries.

F.  Many mistakes have actually been made in the past few years.

G.   Currently about 25% of boys in the country do not finish high school