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SO3 is trigonal planar so that the individual dipoles on the S-O bonds cancel and the molecule has no dipole moment. SF4 has a larger dipole ...
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CHEM1901 2012 - J- 9 June 2012
Marks 3
Sodium stearate dissolves in water to give stearate ions which act as surfactants. They have non-polar (hydrophobic) “tails” that associate with grease and charged, polar (hydrophilic) “heads” that associate with water. This leads to the formation of stable spherical micelles in which the grease molecules are contained within a monolayer of stearate anions with their heads pointing outwards.
CHEM1901 2012 - J- 9 June 2012
C–N bonds are covalent. They are relatively short, strong and highly directional. Mn–CN coordination bonds are due to the donation of the lone pair of electrons on C to the Mn2+. These bonds are weaker, longer and less directional than covalent bonds. [Mn(CN) 6 ]^4 –^ and K+^ are ionically bonded in the solid state due to coulombic attraction between the oppositely charged ions. These bonds are strong but not directional.
The polar molecules are CH 3 Cl, CH 3 F and NF 3. Although the bonds in the other molecules are polar, the overall molecules are non-polar due to their symmetrical shape.
The molecular dipole moments increase in the order:
NF 3 < CH 3 Cl < CH 3 F
This increase is consistent with the difference in the electronegativity of the atoms: C < N < Cl < F.
Marks 3
The solid is less dense than the liquid. The density of the liquid can decrease on cooling. The melting and boiling points are significantly higher than would be predicted from extrapolation of the other group 16 dihydrides. It is capable of dissolving ionic solids to a larger extent than most other liquids.
The shape of molecules can led to biological specificity, eg in smell and in drug action. The shape of molecules also leads to differences in intermolecular forces such as the different boiling points of straight and branched alkanes and the formation of liquid crystal phases in certain molecules.