Gay Lussac’s of combining volumes states that gases react in simple ratio with one another and to volumes of the products provided that temperature and pressure remain constant. In this article, you will understand how to apply this law in calculation by studying the following examples below: 1. 2H 2 + O 2 → H 2 O In the reaction above, what volume of hydrogen would be left over when 300cm 3 of oxygen and hydrogen are exploded in a sealed tube? 1cm 3 of oxygen = 2cm 3 of hydrogen 300cm 3 of oxygen = 2 x 300 = 600cm 3 Volume of left over = 1000 – 600 = 400cm 3 2. Calculate the volume of carbon (II) oxide required to react with 40cm 3 of oxygen. 2CO + O 2 → 2CO 2 1cm 3 of oxygen = 2cm 3 of CO 40cm 3 of oxygen = 2 x 40 = 80cm 3 3. Calculate the volume of residual gases that would be produced when 100cm 3 of sulphur (IV) oxide reacts with 20cm 3 of oxygen 2SO 2 + O 2 → 2SO 3 1cm 3 of O 2 = 2cm 3 20cm 3 of O 2 = 2 x 20 = 40cm 3
Ammonium trioxocarbonate(IV) is an electrovalent compound just like any other ammonium salts. As an electrovalent compound, it has NH+ (ammonium ion) as the cation and CO32-
(trioxocarbonate IV ion or radical) as the anion.
(NH4)2CO3 ------- 2NH4+
+ CO32-
Ammonium trioxocarbonate IV is a white crystal
salt and it is very soluble in water like all other ammonium salts. It decomposes
on heating to produce ammonium, water and carbon (IV)oxide.
(NH4+)2CO3 ---------- 2NH3(g)+
H2O(I) + CO2(g)
Test for the Cation in Ammonium Trioxocarbonate
IV
To test the unknown sample, put the sample into a boiling
tube, add a base or alkali into the boiling tube and heat gently.
Note: All ammonium salts
liberate ammonia when heated with base or alkali.
(NH4)2CO3(s)
+ 2NaOH (aq) ---------- Na2CO3 (aq) + H2O(l) + 2NH3(g)
Test the gas liberated with damp litmus paper, if
it turns red litmus blue, the gas is ammonia. It is so because ammonia gas is
the only alkaline gas known. Smell the gas, If the gas is liberated, the gas has a
pungent smell like that of urine; it means that the compound has ammonium ion
as its cation.
Another test
which can help to confirm if ammonium ion is present in
The unknown substance is the reaction of ammonia
gas with hydrogen chloride gas or hydrochloric acid. Ammonia gas forms a dense
white fume with hydrogen chloride or hydrochloric acid.
NH3(g) + HCl (aq) ------- NHCl(aq)
Dip a glass rod into a dilute hydrochloric acid
then place, it just a little above the rim of the boiling tube containing a mixture of an unknown substance and alkali or base, If the substance contains NH4+ ammonium ion white fume of ammonium chloride
will be formed.
Test for the Anion in Ammonium
Trioxocarbonate IV
The anion in ammonium trioxocarbonate IV is
trioxocarbonate IV ion (radical).
Note:
All trioxocarbonate IV salts liberate carbon (IV) oxide when acid is added to
them.
So, if a dilute hydrochloric acid into the unknown sample
of salt, gas will be liberated. Test the gas with litmus paper, if it turns
blue litmus paper red it is an acidic gas then bubble the gas into lime water. If
it turns the lime water milky, it confirms the presence of carbon (IV) oxide or
trioxocarbonate IV radical.
Ca (OH)2(a) + CO2(g) -------- CaCO3(s)
+ H2O(l)
Continuous bubbling of the gas will turn the lime
water colourless as a result of the presence of calcium hydrogen carbonate (IV)
compound.
CaCO3(s)+ CO2(g)
+ H2O(l) --------- Ca(HCO3)2(aq)
|
|
Test |
Observation |
Inference |
|
a |
C
+ distilled water and shake Very
well then divide into two portions |
C
dissolved to form a colourless solution |
K+,
Na+ and NH4+ Likely
present |
|
B(i) |
To
the first portion add dilute NaOH + heat |
A
gas with a pungent smell like that of urine which turns red litmus paper blue. |
NH3
gas NH4+
present |
|
(ii) |
Dip
a glass rod into dilute HCl and bring it closer to the gas given off in b(i) |
The
gas forms dense white fumes with dilute HCl |
NH4+,
NH3 gas confirmed |
|
C(i) |
To
the second portion, add the BaCl2 solution |
White
precipitate formed |
SO42-,SO32-,
CO32-, likely present |
|
(ii) |
To
the solution in c(i) add dilute HCl |
Forms
a soluble solution with a gas given off which is odourless, colourless and
turns lime water milky |
CO2
gas, CO32-
confirmed |
Note:
The result of this test is still the same if an aqueous solution of ammonium
trioxocarbonate is used.
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