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
Before we go ahead with this analysis, it will be necessary to note that ammonium ferrous sulphate ((NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O) is a double salt which has ammonium ions, iron (II)ions and tetraoxosulphate VI ions. It has six molecules of water of crystallization and it is also a reducing agent. Materials required for the analysis The materials and regents we are going to use in this analysis are as follows: · Dilute hydrochloric acid · Dilute sodium hydroxide solution · Aqueous barium chloride · Red and blue litmus paper · Distilled water · Test tubes and boiling tubes · Acidified potassium dichromate solution · Aqueous ammonia · Dilute tetraoxosulphate VI acid · Source of heat · Glass rod Analysis of Ammonium Ferrous Sulphate To analyse the unknown sample, add some samples of the unknown compound into a test tube then add about 10cm 3 of distilled water and shake