问题 选择题

下列实验操作正确的是(  )

A.测定溶液的pH时,先把pH试纸润湿,后滴被测试液

B.取最少量液体时,一般不超过试管容积的三分之一

C.蒸发时,当蒸发皿中出现较多量固体时立即停止加热

D.读量筒内液体的体积数时,视线与量筒内液面保持水平

答案

A、用pH试纸测定未知溶液的pH时,正确的操作方法为用玻璃棒蘸取少量待测液滴在干燥的pH试纸上,与标准比色卡对比来确定pH.不能用水湿润pH试纸,否则稀释了待测溶液,使溶液的酸碱性减弱,测定结果不准确,故选项说法错误;

B、如果药品的取用,没有说明用量,固体取盖满试管底部,液体取1~2ml,液体药品的最大量是不能超过试管容积的三分之一,故选项说法错误;

C、蒸发时,当蒸发皿中出现较多量固体时立即停止加热,靠余热烘干,故选项说法正确;

D、量取液体时,视线与液体的凹液面最低处保持水平,是凹液面而不是液面,故选项说法错误;

故选项为:C.

单项选择题
单项选择题

Among various programmes, TV talk shows have covered every inch of space on daytime television. And anyone who watches them regularly knows that each one is different in style. But no two shows are more opposite in content, while at the same time standing out above the rest, than the Jerry Springer and the Oprah Winfrey shows.

Jerry Springer could easily be considered the king of" rubbish talk". The contents on his show are as surprising as can be. For example, the show takes the ever-common talk show titles of love, sex, cheating, and hate, to a different level. Clearly, the Jerry Springer show is about the dark side of society, yet people are willing to eat up the troubles of other people’s lives.

Like Jerry Springer, Oprah Winfrey takes TV talk show to its top. But Oprah goes in the opposite direction. The show is mainly about the improvement of society and different quality of life. Contents are from teaching your children lessons, managing your work week, to getting to know your neighbors.

Compared to Oprah, the Jerry Springer show looks like poisonous waste being poured into society. Jerry ends every show with a" final word". He makes a small speech about the entire idea of the show. Hopefully, this is the part where most people will learn something very valuable.

Clean as it is, the Oprah show is not for everyone. The show’s main viewers are middleclass Americans. Most of these people have the time, money, and ability to deal with life’s tough problems. Jerry Springer, on the other hand, has more of a connection with the young adults of society. These are 18 to 21 year olds whose main troubles in life include love, relationship, sex, money and drug. They are the ones who see some value and lessons to be learned through the show’s exploitation.

We can learn from the passage that the two talk shows()

A. have become the only ones of its kind

B. exploit the weaknesses in human nature

C. appear at different times of the day

D. attract different people