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
Qualitative analysis is the type of chemical analysis which its objective is to identify the ions, atoms or functional groups in an unknown substance. To identify the ions, the chemical properties of the unknown substance are determined by carefully reacting the unknown substance with different reagents. By defining what the particular reaction will be if a particular ion is present, the ions that are presence in the solution of the unknown substance can be identified. For example, adding barium chloride in a solution of a compound containing tetraoxosulphate (VI), trioxosulphate (IV) or trioxocarbonate (IV) gives a white precipitate. The precipitate from the last two will dissolve in dilute acid to produce sulphur (IV) oxide and carbon (IV) oxide respectively. These reactions help to differentiate between trioxocarbonate (IV) and trioxosulphate (IV) radicals. Another method employed in qualitative analysis is checking the solubility of the various compounds in water,