Q18.
(a) Iodine has more electrons / iodine is bigger (atom or
molecule) / iodine has bigger Mr / bigger surface area
1
Stronger / more van der Waals forces / vdw / London /
temporarily induced dipole / dispersion forces between
molecules
1
Stronger VdW intermolecular forces = M2
If stated VdW between atoms lose M2
(b) (i)
Mark is for 3 bp and 1 lp attached to N (irrespective of shape)
1
Mark is for 3 bp and 0 lp attached to B (irrespective of shape)
1
NHF2 shape – pyramidal / trigonal pyramid
Accept tetrahedral / triangular pyramid
1
BF3 shape – trigonal planar
Not triangular or triangular planar
1
(ii) 107°
Allow 106-108°
1
(c) Hydrogen bonds
Allow H-Bonds
Not just Hydrogen
Apply list principle eg Hydrogen bonding and dipole-dipole = 0
1
(d) Coordinate / dative covalent / dative
If covalent mark on
If ionic / metallic CE = 0
1
Lone pair / both electrons/ 2 electrons on N(HF2) donated (to BF3)
Direction of donation needed here
1
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