题干

某甲酸溶液中可能存在着甲醛,下列操作能证明的是(   )

A:加入新制的Cu(OH)2加热,有砖红色沉淀产生,证明一定存在甲醛

B:能发生银镜反应,证明含甲醛

C:试液与足量NaOH溶液混合,其蒸馏产物可发生银镜反应,则有甲醛

D:先将试液充分进行酯化反应,收集生成物进行银镜反应,有银镜产生,则含甲醛

上一题 下一题 0.0难度 选择题 更新时间:2018-04-21 08:01:56

答案(点此获取答案解析)

C

同类题2

任务型阅读

The Farmers' Fresh Market

    This morning,I went to the Farmers Market in Burlington ,Vermont. I didn't know what the Farmers Market is or how to get there.____

    First ,I had to decide how to go there,and I chose both to walk and to take a bus. When I went,I would walk and when I came back,I would take a bus.____

Walking to the market in this city,I was surprised because every house was beautiful,and they were all arranged in good order. In Korea's cities,most houses are not like that,and many apartments are like boxes which often screen off beautiful views like hills and mountains. Also,every road is not straight and narrow.____

    ____It was a very small market,but a very interesting one. I don't know why farmers go there to sell vegetables or why people go there to buy them because there are many more products in large supermarkets.____

    Also ,all the things sold there were very novel. In addition to fresh food,there was homemade food and many other things such as woolen blankets,quilts ,and wooden products.

    I wanted to buy some of them,but I didn't need them,so I just looked at them. It was a very exciting experience.

A. I visited a flower stand at the market.

B. Anyway,I was able to find the Farmers' Market.

C. So, to me, this American town was very impressive.

D. I decided to go early because the market is held in the morning.

E. I knew that it would take a long time to walk,but I wanted to see an American town.

F. I was attracted by the comfortable houses where they lived and the cars that they drove.

G. I think the reason is that the ones sold in the Farmers' Market are fresher and cheaper.