问题 选择题

为除去镀在铝制品表面的铜镀层,可选用的试剂是(   )

A.稀硝酸

B.浓硝酸

C.浓硫酸

D.浓盐酸

答案

答案:B

稀硝酸既能溶解铜,也能溶解铝,不符合要求。浓硝酸在常温下可溶解铜,不能溶解铝(钝化),符合要求。浓硫酸在常温下既不能溶解铜,也不能溶解铝;在加热条件下既能溶解铜,也能溶解铝,不符合要求。浓盐酸不能溶解铜,能溶解铝,不符合要求。

写句子

我会按要求改写句子。     

1.难道我们不该珍惜时间,努力学习吗?(改为陈述句)

                                                                                                                                 

2.机灵的小松鼠在树上高兴地跳着叫着。(缩句)

                                                                                                                                 

3.小姑娘把水罐交给了母亲。(改“被”字句)  

                                                                                                                                 

4.下课后,我被老师叫到了办公室。(改“把”字句)

                                                                                                                                 

5.白云飘来飘去。(扩句)

                                                                                                                                 

填空题