有NaCl和NaI的混合物共26.7 g,溶于水,通入足量氯气后,蒸干、灼烧,固体质量变为17.55 g。求原混合物中氯化钠的质量分数。
秦灭六国的根本原因是( )A.社会经济军事实力强大 B.社会制度最先进C.秦始皇个人雄才大略 D.适应国
–Why?This is simply a common bike! –_____ sir.It’s our special offer today. A. Don’t mention it B. Let me see C. So it is D. Neither do I
下列有关说法错误的是( )A.电源是提供电压的装置 B.电压是形成电流的原因C.电路两端只要有电压就一定有电流 D.电流是电荷的定向
已知:①CH3OH(g) +3/2O2(g)=CO2(g)+2H2O(g) △H=-akJ·mol一1 ②CH4(g)+2O2(g)=CO2(g)+2H2O(g) △H=-bkJ·mol一1 ③CH4(g)+2O2(g)=CO2(g)+2H2O(1) △H=-ckJ
鉴别下列各组物质的方法不正确的是 选项鉴别的物质鉴别的方法 A纯水和矿泉水观察是否澄清 B二氧化碳和一氧化碳点燃,观察是否能燃烧 C水和过氧
_______ careful enough, he made several careless mistakes in the exam. A. Being not B. Not being C. He was not D. Wasn’t