ENERGETICS 83
In view of your comments, discuss why sodium chloride is soluble
in water.
(b) The ionisation energies (expressed in electron volts (eV) of
the elements in the first short period are: Li, 5.4; Be. 9.3; C.
11.3;N. 14.5 ;O. 13.6; F. 17.4; Ne. 21.6.
(C,A)
- Comment on the following:
(a) KBr is a stable compound although the process K(g) -h Br(g)
-» K + (g) + Br~(g) is endothermic.
(b) Silver fluoride is the only silver halide that is appreciably
soluble in water.
(c) Nitrogen forms one endothermic chloride NC1 3 but phos-
phorus reacts with chlorine to give two chlorides PCl^ and
PC1 5.
(O. Schol.)- Give an account of the principles underlying the extraction of
metals from their oxides, illustrating your answer by specific
examples.
(Liverpool B.Sc., Part 1)