问题 填空题

【化学——化学与技术】 废旧硬质金刀具中含碳化钨(WC)、金属钴(Co)及少量杂质铁,利用电解法可回收WC和Co。工艺流程简图如下:

答案

参考答案:

Co

2

O

3

+3H

2

=2Co+3H

2

O

材料题

读下列材料:

“忆昔开元全盛日,小邑犹藏万家室。 稻米流脂粟米白,公私仓廪俱丰实。”一一杜甫

(1)上述材料反映了唐朝哪一时期的繁荣景象?

                                                                                                                                                             

(2)为什么引文中称“开元全盛日”?

                                                                                                                                                             

(3)为何会在“开元”时进入全盛时期?

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

单项选择题