Which statement best describes the intramolecular bonding in HCN(l)?

A.     Electrostatic attractions between \({{\text{H}}^ + }\) and \({\text{C}}{{\text{N}}^ - }\) ions

B.     Only van der Waals’ forces

C.     Van der Waals’ forces and hydrogen bonding

D.     Electrostatic attractions between pairs of electrons and positively charged nuclei

D

This was by far the most challenging question on the paper, with a difficulty index of 24%, and many teachers commented about it on the G2 form. It appears that at SL many candidates were not familiar with the term “intramolecular” and in addition failed to assume that the pure liquid compound was being referred to, both of which seemed to create a degree of confusion. It did however appear more accessible to the better candidates, with a discrimination index of 0.18.