Download - 2 hydrogen
Objectives
To enumerate the properties of
hydrogen
To relate the properties of
hydrogen to its industrial uses
OCCURENCE OF
HYDROGEN
most abundant element in the
universe
90% of the atoms of sun and stars
11% by mass H in water
9th most abundant element on the
earth’s crust
3 isotopes of hydrogen:
1. Protium, H-1
99.9844%
2. Deuterium, H-2
0.0156%
3. Tritium, H-3
very small
PROPERTIES OF
HYDROGEN
It is a diatomic gas under most
conditions, H2
It is colorless, odorless, tasteless gas at
normal temperatures
It does not support combustion but it
burns
It is a reactive element.
a) It reacts with active metals
forming compounds called
hydrides.
Examples : NaH, CaH2
b) It is displaced from non-oxidizing
acids by metals above it in the
activity series of metals
Example:
Zn(s) + HCl(aq) ZnCl2 +
H2(g)
see p. 136 Central Science
c) It is displaced vigorously from water
by metals located at the top of the
activity series of metals.
COMMERCIAL PREPARATION OF
HYDROGEN
1. Water Gas Method
Reactions: Ni
C(S) + H2O(steam) CO(g) +
H2(g)
water gas
CO(g) + H2(g) + H2O(steam) CO2(g) + 2
H2(g)
2 methods of separating CO2 & H2
mixture:
*Passing the CO2 and H2 mixture through water under pressure
*Passing the CO2(g) and H2(g) mixture over lime (CaO).
CO2(g) + H2(g) + CaO(s) CaCO3(s) + H2(g)
2. Steam-Hydrocarbon Method
Ni
CH4(g) + 2 H2O(steam) CO2(g) + 4 H2(g)
heat
*The hydrogen is separated from carbon
dioxide as in the water gas method.
USES OF HYDROGEN
1.It is used as fuel for rockets in
space
2 a. It is used in making other
compounds such as ammonia,
hydrochloric acid and methanol
b. It is used in the catalytic
hydrogenation of oils and semi-
solid fats for the making of
margarine, household shortening
and soap
c. It is used as a reducing agent for the
production of certain metals from their
metal oxides
To illustrate:
CuO(s) + H2(g) Cu(s) + H2O
WO(s) + H2(g) W(s) + H2O