问题
选择题
Although metals________widely in qualities such as strength and hardness,they all have certain qualities in________.[ ]
A. vary;general
B. differ;common
C. react;particular
D. refer;detail
答案
答案:B
Although metals________widely in qualities such as strength and hardness,they all have certain qualities in________.[ ]
A. vary;general
B. differ;common
C. react;particular
D. refer;detail
答案:B
将一定量的乙醇和氧气置于一个完全封闭的容器中引燃,反应生成二氧化碳、水蒸气和一种未知物X.测得反应前后物质的质量如下表:
物质 | 乙醇 | 氧气 | 二氧化碳 | 水 | X |
反应前质量/g | 4.6 | 8 | 0 | 0 | 0 |
反应后质量/g | 0 | 0 | 4.4 | 5.4 | m |
A.表中m的值无法确定
B.X可能是该反应的催化剂
C.增加氧气的量可以减少X的生成
D.物质X一定含有碳元素,可能含有氢元素