题干

有一瓶无色气体,可能含有CO2、HBr、SO2、HCl、NO2中的若干种,将其通入氯水中,得无色透明溶液。将此溶液分成两份,向其中一份加入BaCl2溶液,有白色沉淀产生;向另一份中加入硝酸酸化的AgNO3溶液,也有白色沉淀产生。则下列结论正确的是

A:肯定有SO2、HCl

B:一定没有CO2、HBr、NO2

C:可能有HBr、CO2

D:一定有SO2 ,可能有HCl、CO2

上一题 下一题 0.0难度 选择题 更新时间:2014-03-19 10:53:55

答案(点此获取答案解析)

D

同类题5

阅读理解

    Teachers in some secondary schools in Britain are worried that their job may become impossible shortly unless something can be done to restore discipline in the classrooms. In the problem schools, mostly in large cities, a small minority of teenage pupils disturb lesson to such an extent that the teacher can no longer teach their classes effectively.

    Some people consider that the permissive (随意) nature of modern society is responsible for such kind of behavior. Small children who are continuously encouraged to express themselves without reservation are naturally unwilling to accept school discipline when they grow older. Furthermore, modern teaching techniques) which appear to stress personal enjoyment at the expense of serious study work, might be teaching the child to put his own interests before his duties to the community in which he lives.

    Perhaps the problem can be solved by improving facilities for the moral guidance of these difficult children or by better cooperation between the schools and the parents—for the parents may be mainly responsible for the bad behavior of their youngsters. Violence at home, violence and crime on TV make some children turn violence themselves.

    But some of the teachers believe that there ought to be a return to more “old fashioned” methods. At present, in some school teachers are even not allowed to punish a child who does something bad and wrong. Physical punishment is not permitted now. People are too soft on children these days. It seems that children can do whatever they like at school while the teachers can't do anything to punish them. I don't know why the schools authority abandoned some of the effective punishments that worked well. Things like that didn't happen when we were at school because the teachers kept those problem students under control by using a stick.