丁酸乙酯(化学式为C 6 H 12 O 2 )是一种无色、具有菠萝香味的液体,常用作食品、饮料的调香剂.根据丁酸乙酯的化学式计算: (1)丁酸乙酯的相对分子质量是______; (2)丁酸乙酯中碳、氢、氧三种元素的质量比是(化成最简整数比)______; (3)丁酸乙酯中碳元素的质量分数是(计算结果精确到0.1%)______.
【单选题】听力原文: An election year is one in which all four numbers are evenly divided by four (1944, 1940, etc. ),. Since 1840, American presidents elected in years ending in zero have been destined to die in of...
【单选题】听力原文: An election year is one in which all four numbers are evenly divided by four (1944, 1940, etc. ). Since 1840, American presidents elected in years ending in zero have been destined to die in off...