#6.Answer should be C not D
Ethan (C2H6)has the C-C single bond, Ethene (C2H4) has C-C doublebond, and Ethyne (C2H2) has C-C triple bond. Therefore, Ethan has weakest bond and ethyne has the strongest bond.
#27.
Answer should C not D.
Nitrogen molecule has 3 pairs of bonding electrons (triple bond between nitrogens) and 2 pairsof non-bonding electrons (1 pair from each nitrogen).