This is a video tutorial in the Education category where you are going to learn how to use and understand chemical equilibrium in Chemistry. This video answers a question about the contact process. This is a process by which sulphuric acid is made where they take sulphur, react it with oxygen to make sulphur dioxide and react it with more oxygen to make sulphur trioxide. The equation here is 2SO2 + O2 will give us 2SO3. This reaction is exothermic, that means it will give out energy in the form of heat. To understand why this happens we got to see the Le Chatilier principle. It says, if there is stress on a system then the system will oppose the stress. You can now watch the video for further instructions.