Which pair of formulas correctly represents a molecular formula and its corresponding empirical formula?

(1) C2H2 and CH (3) C4H6 and CH

(2) C3H4 and CH2 (4) C5H8 and C2H2

Answer=1

C2H2 is correct when writing the molecular formula, but when we write the empirical formula, we use the smallest whole number ratios ...

So C2H2 (2 Carbons:2Hydrogens) becomes CH (1Carbon:1Hydrogen)

The other ones have an incorrect empirical formula ...

2. C3H4 is already in empirical form, so it should stay C3H4

3. C4H6 in empirical form should be C2H3

4. C5H8 is also already in empirical form, so it should stay C5H8

(1) C2H2 and CH is your answer. An empirical formula only depicts the ratios of how many atoms of each element exist in the compound, and only in this choice is the ratio correct for the molecular formula.