Im having trouble solving this question again can someone explain this to me please thank you

Which of the following pairs does not share the same empirical formula?

CH2O and C3H6O3

PbCl2 and PbCl4

NO2 and N2O4

C3H12 and CH4

The other answerer is a moron. An empirical formula is the most reduced formula. The 1st is the same because the second can have a three taken out of all the elements so it becomes the same as the beginning. The second do not have the same empirical formula because they are already empirical formulas. And the third and forth have same reasoning as the first.

Only the second pair does not share the same emperical formula. An emperical formula is the simplest whole number ratio of atoms in a compound. Here is an example: the chemical formula for glucose is C6H12O6. It's emperical formula would just be CH2O (just the ratio of atoms) so above only the second pair does not share the same emperical formula.

1st and 3rd and 4th

This one is the correct answer:

PbCl2 and PbCl4