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:

17) The possible number of alkynes with the formula C₅H₈ is:

18) How many isomers of C₅H₁₁OH will be the primary alcohols?

19) The maximum number of acyclic isomers for an alkene with molecular formula C₄H₈ is: