August 2018 NY Regents Chemistry Exam
35 The empirical formula for butene is
(1) CH2
(2) C2H4
(3) C4H6
(4) C4H8
Solution: An empirical formula is a formula with the simplest ratio of atoms. This means the subscripts in the formula can not be divide any further. For C2H4, we can divide both subscripts by 2 to get CH2, eliminating choice 2. For C4H6 we can divide both subscripts by 2 to get C2H3, eliminating choice 3. For choice 4, C4H8, we can divide both numbers by 4, eliminating it as well. CH2 is the only molecule that cannot be divided any further.
Answer:1
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