1st Year Chemistry Chapter 8 Notes

• State Law of Mass Action: The rate at which the reaction proceeds is directly proportional to the product of the active masses of the reactants. General reaction Consider a general reaction in which A and B are the reactants and C and D are the products.
• Applications of Equilibrium Constant
• Difference between equilibrium constant and equilibrium position
• State The Le-Chatelier’s Principle
• Effect on Kc and equilibrium position
• Reactions not affected by pressure/volume change
• Temperature change at equilibrium
• Effect of temperature on equilibrium: Temperature change at equilibrium At equilibrium stage, if we take out heat and keep the system at this new lower temperature, the system will readjust itself, so as to compensate the loss of heat energy. More of CO and H2O molecules will react to form CO2 and H2 molecules, thereby, liberating heat because reaction is exothermic in the forward direction. It means by decreasing temperature, we shift the initial equilibrium position to the right until a new equilibrium position is established. Heating the reaction at equilibrium will shift the reaction to the backward direction because the backward reaction is endothermic.
• Applications of Chemical Equilibrium in Industry: Industrial conditions Industrial conditions denoted by circle are between 200 and 300 atmospheres at about 400 oC. Low temperature yield The yield of NH3 is favoured at low temperature, but the rate of its formation does not remain favourable. Optimum conditions The optimum conditions are the pressure of 200-300 atm and temperature around 673 K (400 oC). The catalyst is the pieces of iron crystals embedded in a fused mixture of MgO, Al2O3 and SiO2. Equilibrium mixture The equilibrium mixture has 35% by volume of ammonia. Cooling of equilibrium mixture The mixture is cooled by refrigeration coils until ammonia condenses (B.P = -33.4 oC) and is removed. Recycling of gases Boiling points of nitrogen and hydrogen are very low they remain in the gaseous state and are recycled by pumps back into the reaction chamber. Advantages of Haber’s process Nearly 13% of all nitrogen fixation on earth is accomplished industrially through Haber’s process. This process synthesizes approximately 110 million tons of ammonia in the world. About 80% of this is used for the production of fertilizers and some is used in manufacture of explosives or the production of nylon and other polymers.
• Define Common Ion Effect with example
• Effect of volume change at equilibrium According to the above equation, when volume is increased, then ‘x’ has to be decreased to keep Kc constant. The decrease of x means that reaction is pushed to the backward direction. From the amount of the increase in volume, we can calculate the amount of x which has to be decreased to keep Kc constant.
• effect of pressure on equilibrium constant: Increasing the pressure on the above reaction at equilibrium will decrease the volume and the value of Kc will increase. In order to keep the value of Kc constant the reaction will move in the forward direction.
• Write a note on synthesis of ammonia by Haber’s process keeping in mind the applications of chemical equilibrium in industry.
• State le-Chatelier’s principle. Describe the effect of change in temperature of a system in equilibrium by this Principle.
• State le-Chatelier’s principle. How is this principle used to explain the effect of change in concentration on equilibrium constant of a reaction?
• What is common ion effect? Explain it.