问题 选择题

区分下列各组物质的操作方法中,不正确的是

A.软水和硬水:滴加肥皂水

B.铁粉和碳粉:滴加稀硫酸

C.碳酸钙和氧化钙:滴加水

D.一氧化碳和二氧化碳:放入干燥的石蕊纸花

答案

答案:D

题目分析:根据要鉴别的两物质的性质分析判断。

A、硬水中含有较多可溶性钙镁化合物,而软水中不含或含有较少可溶性钙镁化合物,分别往其中滴加肥皂水,浮渣多而泡沫少的为硬水,泡沫多的为软水,故可以区分;

B、铁属于H前的活泼金属,能与稀硫酸发生置换反应而放出氢气,而碳不与稀硫酸反应,故可以用稀硫酸进行区分;

C、由于氧化钙能与水反应放出大量的热,而碳酸钙不能,故可以用加水的办法进行区分;

D、一氧化碳和二氧化碳,都不能使干燥的石蕊纸花变色,故不能区分。故选D

点评:本题属于物质的鉴别题,解题的关键是要掌握所要鉴别物质的性质,尤其是物质的特殊性质,然后利用反应产生的不同现象来加以鉴别。

单项选择题

The Man of Many Secrets—Harry Houdini—was one of the greatest American entertainers in the theater next century. He was a man famous for his escapes—from prison cells, from wooden boxes floating in rivers, from locked tanks full of water. He appeared in theaters all over Europe and America. Crowds came to see the great Houdini and his "magic" tricks.

Of course, his secret was not magic, or supernatural powers. It was simply strength. He had the ability to move his toes as well as he moved his fingers. He could move his body into almost any position he wanted.

Houdini started working in the entertainment world when he was 17, in 1891. He and his brother Theo performed card tricks in club in New York. They called themselves the Houdini Brothers. When Harry married in 1894, he and his wife Bess worked together as magician and assistant. But for a long time they were not very successful. Then Harry performed his first prison escape, in Chicago in 1898. Harry persuaded a detective to let him try to escape from the prison, and he invited the local newspapermen to watch.

It was the publicity that came from this that started Harry Houdini’s success. Harry had fingers trained to escape from handcuffs and toes trained to escape ankle chins. But his biggest secret was how he unlocked the prison doors. Every time he went into the prison cell, Bess gave him a kiss for good luck—and a small skeleton key, which is a key that fits many locks, pass quickly from her mouth to his.

Harry used these prison escapes to build his fame. He arranged to escape from the local prison of every town he visited. In the afternoon, the people of the town would read about it in their local newspapers, and in the evening every seat in the local theater would be full. What was the result World-wild fame, and a name remembered today.

According to the passage, Houdini’s success in prison escapes depends on ()。

A. his special tricks and supernatural powers

B. his unusual ability and a skeleton key

C. his magic tricks and unhuman powers

D. his wisdom and magic tricks

选择题