The reagent(s) used for softening the temporary hardness of water is (are)

The total number of cyclic isomers possible for a hydrocarbon with the molecular formula C₄H₆ is

The synthesis of 3-octyne is achieved by adding a bromoalkane into a mixture of sodium amide and and alkyne

The bond energy (in kcal mol^-1) of a C-C single bond is approximately