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
This is
a type analysis which involves the identification of the ions ( cation and
anion) in a given inorganic substance. Thus, Qualitative analysis deals with
the identification of the compound. To effectively identify the ions, it is necessary
to be able to observe the presence of any chemical reaction which is normally
recognized by
·
Colour change
·
Evolution of gas
·
Precipitation
Colour Change:
colour change is associated with transition metal ions. The major cause of the
colour in transition metal ions is electronic transition within the d-block
level. The colour of light which show, is the colour of light which is reflected
by the ion. This change of transition metal ions is common when they form a bond
with water or ammonia. It is important to note that zinc does not form coloured
ion, this is because zinc has completely filled the d orbital, but zinc is yellow when
hot and white when cold.
Evolution
of gas: This is identified by the formation of bubbles
in the solution or effervescence. When this occurs, notice the colour and odour
of the gas. Test the gas with damp litmus blue and red litmus papers, before
carrying out any specific tests on it.
Precipitation: this is the name given to a type
of reaction in which insoluble solid is formed from solution. The insoluble
particles formed are called precipitates. In qualitative analysis, it is
necessary to note the colour and nature of the precipitate because these serve
as a guide towards the identification of ions presence in the solution, semi-solid
precipitates are called gelatinous precipitates
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