In an organic compound, C 68.5% and H 4.91% . Which empirical formula is correct for it? (CPMT 2009) (a) C H (b) C H O (c) C H O (d) C H O Ans. (b) Sol. Element At. Percent No. of Simple molar wt. composition moles ratio C 68.5 68.5 5.708 1.67 = 5.708 = 3.41 × 2 7 H 4.91 4.91 = 4.91 4.91 1.67 = 2.95 × 2 6 O (100-68.5+4.91) 26.59 1.67 1.67 = 26.59 = 1.67 = 1 × 2 2 Hence, the empirical formula of the compound is C H O . EXERCISE - 2 : Previous Year Questions