在80℃时，物质A的溶解度比B小。分别取等质量的A、B两物质的饱和溶液，降温至30℃，析出A、B晶体的质量分别为mg和ng（A、B均不含结晶水）。下列判断正确的是
A．80℃时，A饱和溶液与B饱和溶液相比，前者所含溶质的质量一定比后者小
B．30℃时，若A的溶解度比B大，则m一定小于n
C．30℃时，若A的溶解度比B小，则m一定大于n
D．30℃时，A 饱和溶液与B饱和溶液相比，后者溶质的质量分数一定比前者大
答案：B
题目分析：A选项是错误的叙述，因为没有说明溶液的质量；B选项由题意可知，是正确的叙述，答案选择B；C选项是错误的叙述，因为降温前后溶解度都小，那就看溶解度受温度影响的大小无法确定；D选项是错误的叙述，大小关系要看m和n的关系确定．
第四部分 任务型阅读（共10小题，每小题1分，满分10分） 阅读短文，根据所读内容在文后76~85的空格里填上适当的单词或短语。注意：每空不超过3个单词。 Many children first learn the value of money by planning the use of an allowance (零用钱). The purpose of it is to let children learn from experience at an age when financial mistakes are not very costly. The amount of money that parents give to their children to spend differs from one family to another. Timing is another consideration. Some children get a weekly allowance. Others get a monthly allowance. In any case, parents should make it clear what their child expects to pay for with the money. At first, young children may spend all of their allowances soon after they receive them. If they do this, they will learn the hard way that spending must be done within a budget (预算). Parents are usually advised not to offer more money until the next allowance. The object is to show young people that budgeting means making choices between spending and saving. Older children may be responsible (有责任感的) enough to save money for larger costs, like clothing or electronics. Sometimes paying children to do extra work around the house can be useful. Allowances give children a chance to experience the three things they can do with money. They can share it in the form of gifts or use it to do good things; they can spend it by buying things they want; or they can save it. Saving helps children understand that costly goals require sacrifice (舍弃) — you have to cut costs and plan for the future. Requiring children to save part of their allowances can also open the door to future saving and investing. Many banks offer services to help children and teenagers learn about personal finances. For example, one dollar invested at two percent interest (利息) for two years will earn two cents in the first year. The second year, the money will earn two percent of one dollar and two cents, and so on. That may not seem like a lot. But over time it adds up. Title: 76.______________
|