Question

Which of the following pairs share the same empirical formula?

CH4 and C2H4

PbCl2 and PbCl4<----- my answer, correct?

NO2 and N2O4

C2H6 and CH4

Answer 1

No, the empirical formula is the lowest whole number ratio of the molecular formula. Example: C6H12O6 goes to CH2O

In this case, the third option is the correct one. 

Answer 2

Answer: The pair which shares the same empirical formula is $NO_2\text{ and }N_2O_4$.

Explanation: Empirical formula is defined as the chemical formula in which the elements in the compound are present in simplest ratio.

So, from the given pairs, only $NO_2\text{ and }N_2O_4$ shares the same empirical formula which is $NO_2$