问题 选择题

鉴别NaCl、NaBr、NaI三种溶液可以选用的试剂是(  )

A.氯水、CCl4

B.淀粉溶液

C.溴水

D.碘水

答案

A.氯水与NaBr、NaI反应分别生成溴、碘,则再加四氯化碳,出现不同现象,分别为分层后下层橙红色、分层后下层为褐色,现象不同,可鉴别,故A正确;

B.均不与淀粉反应,现象相同,不能鉴别,故B错误;

C.只有NaI与溴水反应,不能鉴别NaCl、NaBr,故C错误;

D.均不与碘水反应,现象相同,不能鉴别,故D错误;

故选A.

材料题

       魏主下诏,以为“北人谓土为拓,后为跋。魏之先出于皇帝,以土德王,故为拓跋氏。夫土者,黄中之色,万物之元也,宜改姓元氏。”

(1)“魏主”是谁?

                                                                                                                                                            

(2)魏主的这个诏令提出了什么方面的改革?类似的改革还有哪些方面?

                                                                                                                                                            

                                                                                                                                                            

(3)这此改革发生在哪一重大历史事件之后?有什么作用?

                                                                                                                                                            

                                                                                                                                                            

单项选择题