问题 单项选择题

适合酸、碱或两性化合物分离精制的方法是()

A.结晶或重结晶

B.溶剂沉淀法

C.酸碱沉淀法

D.盐析法

E.透析法

答案

参考答案:C

解析:适合酸、碱或两性化合物分离精制的方法是酸碱沉淀法,故1题答案选C。利用物质在溶剂中因温度不同而溶解度发生改变使之分离的方法是结晶或重结晶,故2题答案选A。根据分子量大小不同进行分离的方法是透析法,故3题答案选E。

配伍题 B型题
单项选择题

People have good reason to care about the welfare of animals. Ever since the Enlightenment, their treatment has been seen as a measure of mankind’s humanity. It is no coincidence that William Wilberforce and Sir Thomas Foxwell Buxton, two leaders of the movement to abolish the slave trade, helped found the Royal Society for the Prevention of Cruelty to Animals in the 1820s. An increasing number of people go further: mankind has a duty not to cause pain to animals that have the capacity to suffer. Both views have led people gradually to extend treatment once reserved for mankind to other species.

But when everyday lives are measured against such principles, they are fraught with contradictions. Those who would never dream of caging their cats and dogs guzzle bacon and eggs from ghastly factory farms. The abattoir and the cattle truck are secret places safely hidden from the meat-eater’s gaze and the child’s story book. Plenty of people who denounce the fur-trade (much of which is from farmed animals) quite happily wear leather (also from farmed animals).

Perhaps the inconsistency is understandable. After hundreds of years of thinking about it, people cannot agree on a system of rights for each other, so the ground is bound to get shakier still when animals are included. The trouble is that confusion and contradiction open the way to the extremist. And because scientific research is remote from most people’s lives, it is particularly vulnerable to their campaigns.

In fact, science should be the last target, wherever you draw the boundaries of animal welfare. For one thing, there is rarely an alternative to using animals in research. If there were, scientists would grasp it, because animal research is expensive and encircled by regulations. Animal research is also for a higher purpose than a full belly or an elegant outfit. The world needs new medicines and surgical procedures just as it needs the unknowable fruits of pure research.

And science is, by and large, kind to its animals. The couple of million (mainly rats and mice) that die in Britain’s laboratories are far better looked- after and far more humanely killed than the billion or so (mainly chickens ) on Britain’s farms. Indeed, if Darley Oaks makes up its loss of guinea pigs with turkeys or dairy cows, you can be fairly sure animal welfare in Britain has just taken a step backwards.

In the text, a comparison is made so as to()

A. abolish the slave trade

B. elaborate a higher purpose of animal research

C. warn that mankind has a duty not to cause pain to animals

D. assert that science is, by and large, kind to its animals