118 HYDROGEN
- Outline one method for the manufacture of hydrogen from
either crude oil or natural gas. State two important uses of hydrogen.
Give explanations and illustrate reactions for the following state-
ments.
(i) The hydrides of the elements Na, P, S, Cl, show increasing
acidity with increasing atomic number,
(ii) The hydrides of the elements F, Cl, Br, I, show increasing
reducing power with increasing atomic number.
(C, A)- Discuss the following observations:
(a) The boiling point of methane is considerably lower than that
of the corresponding silicon hydride (SiH 4 , monosilane),
whereas the boiling points of ammonia and of water are higher
than those of phosphine and of hydrogen sulphide respectively.
(b) Aniline is a weaker base than ammonia, but ethylamine is a
stronger base than ammonia.
(c) 1M aqueous solutions of hydrogen chloride, hydrogen
bromide and hydrogen iodide have pH values of 0.09, 0.06
and 0.02 respectively, whereas the pH of a 1 M aqueous
solution of hydrogen fluoride is 1.7.
(d) Ionic compounds are normally readily soluble in water, but
do not dissolve well in organic solvents.