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
Question C and D are samples of two different simple salts. Carry out the following exercises on them. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test. A) Heat about one half of C in dry test tube until no further change is observed. Allow to cool B) (I) to the cooled residue from (a) above, add about 5 cm 3 of dilute hydrochloric acid and warm. (II) to about 2cm 3 of the clear solution from (b)(I) above, add aqueous ammonia in drops until it is excess. C) Put all D in a boiling tube and add about 10 cm 3 of distilled water. Shake thoroughly and divide into two portions. D) (I) to the first portion from (C) above, add about 2 cm 3 of barium chloride solution, followed by dilute hydrochloric acid in excess. Warm the mixture. (II) to the second portion from ( C) above, add 2 to 3 drops of acidified potassium tetraoxomanganate (VII) solution and shake. ( The question is credit t