12) The molecular formula of a saturated compound is C₂H₄Cl₂. The formula permits the existence of two:

13) But−1−ene and cyclobutane exhibit:

14) C₇H₈O shows how many isomers?

15) The type of isomerism found in urea molecule is:

16) On evaporation of an aqueous solution of ammonium cyanate, we get urea. This is the class of reaction known as: