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
The rate of a chemical reaction is the number of moles of reactants converted or products formed per unit time. It varies from one chemical reaction to another because some chemical reactions are faster than others. The rate at which a reaction occurs and its control are significant in industries because they are the factors that determine if the reaction will make economic sense or not. How to measure the rate of chemical reaction Consider a reaction between irons and dilute hydrochloric acid Fe (s) + 2HCl (aq) → FeCl 2(aq) + H 2(g) As the reaction proceeds, the iron is used up and iron (II) chloride and hydrogen gas are formed. The rate of the chemical reaction between iron and the acid can be determined by: · Taking a given mass of iron · Adding an excess of hydrochloric acid · Noting the time taken for all the iron to disappear or react The rate of the chemical reaction can be calculated by: Rate of chemical reaction = amount