问题 选择题

下列混合物的分离方法正确的是(  )

A.食用油和水,用蒸馏法分离

B.食盐中的泥沙,用溶解、过滤法分离

C.提取碘水中的碘,可用过滤的方法分离

D.氢氧化铁胶体中的氯化钠溶液,用半透膜分离

答案

A、食用油和水互不相溶,应用分液的方法分离,而蒸馏用来分离沸点不同的物质,故A错误;

B、食盐溶于水,泥沙不溶于水,溶解、过滤之后还应蒸发才能得到食盐,实现真正意义上的分离,故B错误;

C、过滤适用于分离固液混合物,碘溶于水,但在有机溶剂中的溶解度比在水中大,可用萃取的方法分离,故C错误;

D、胶体粒子不能透过半透膜,溶液溶质粒子可透过半透膜,可用渗析的方法分离,故D正确.

故选D.

单项选择题
单项选择题

Just how does a person arrive at an idea of the kind of person that he is He develops this (1) of self through a gradual and complicated (2) which continues throughout life. The notion is an (3) that one establishes only with the help of others. (4) the elementary knowledge that one is short or tall is a comparative judgment that we cannot make (5) we have the opportunity to (6) ourselves with others. One’s idea of qualities which are harder to (7) is even more dependent upon other people’s ideas.

Whether one is intelligent, or stupid; attractive, or ugly; these and many other ideas of the self are (8) from the reactions of people with whom we (9) This process of (10) the nature of the self from the reaction of others has been labeled the "Looking-glass Self" by Cooley, who carefully analyzed this psychological (11) of self-discovery.

Just as the picture in the mirror gives an image of the physical self, (12) the perception of the reactions of others gives an image of the social self. We know, (13) , that we are good at certain things and not at others. This (14) came to us from the reactions of other persons, first our parents and then other individuals (15) in life. It should be remembered that, as other people’s reactions could be (16) and understood in more than one way, the looking-glass self with which the individual (17) may easily differ from the image others have actually formed of his (18) Clearly, it is our perception of the responses of others and not their (19) responses that (20) our self-image, and these perceptions are often not accurate.

15()

A.sooner

B.later

C.earlier

D.former