区别棉花和羊毛的最简单的方法是_刷题宝

题干

区别棉花和羊毛的最简单的方法是（　　）

A：加入稀硫酸后加热使之水解，检验水解产物能否与新制Cu(OH)₂反应

B：浸入浓硝酸后，观察其颜色是否变黄色

C：在火中灼热，闻其是否有烧焦羽毛的气味

D：通过化学方法测其组成中是否含有硫、氮等元素

上一题下一题 0.0难度选择题更新时间:2020-04-07 11:48:05

答案(点此获取答案解析）

C

同类题1

拼一拼，写一写

gāng cái	míng tiān	yì tóng	xué shēng
____	____	____	____

同类题2

词汇检测

根据下列句子及所给汉语注释或通过上下文，在答题卡上标有题号的横线上，写出空缺处各单词的正确形式。每空只写一词。

Helen ____ (点头) with a smile when she met me.

Becky ____ (明智地) decided to tell us the truth.

Justin lay back and enjoyed the ____ (安宁) of the summer evening.

The bank is ____ (在…对面) the supermarket, on the other side of the road.

My cousin used to be very interested in ____ (收集) postcards.

Edison is one of the greatest____ (发明家) in the world.

Mr. Green often ____ (惩罚) his children by not letting them play games.

— Thanks for lending me the book Black Beauty.

— Don't ____ it.

— What's the ____ of the elephant?

— About two tons.

— Have you drunk all the milk?

— Yes. Look, the bottle is ____ now.

同类题3

阅渎右图漫画。锯树人的错误在于

同类题4

已知{a_n}为等差数列，前n项和为S_n（n∈N⁺），{b_n}是首项为2的等比数列，且公比大于0，b₂+b₃=12，b₃=a₄﹣2a₁，S₁₁=11b₄．

（Ⅰ）求{a_n}和{b_n}的通项公式；

（Ⅱ）求数列{a_2nb_2n_﹣₁}的前n项和（n∈N⁺）．

同类题5

阅读理解

Different types of maps have different uses. Tourist maps, for example, have signs to show places of interest in an area. When tourists read these maps, it is easy for them to find where to go and what to see in a place and it is easy for them to go and find their ways to these places.
	Road maps show large areas so that people can plan long journeys. Different types of roads are given different numbers. For example, if you want to go to Wood Green, you just follow No. 621 Road and keep looking at the road signs.
Distribution maps (分布图) use colors or signs to show facts about an area. For example, where different languages are spoken, how many people live in an area, how cold and hot some places are, or whether a place is short of water.
	Some maps, such as railway maps, use straight lines to show everything. This is easy for people to read. Trains are fast. People don't have to think about small places they go past. They just need to know the two ends of their trips.

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