2.2 Equilibrium & Yield

• When at equilibrium, the rate of the forward reaction = rate of backward reaction. For equilibrium systems to exist from chemical reactions, they need to be in a closed system with a constant temperature to prevent any other matter to enter or exit, meaning the concentrations of reactants and products can stabilise over time. 
• Kc = equilibrium constant which is a ratio of the forward/backward reaction rates - a measure of yield 

  If Kc > 1, the proportion of products to reactants is higher, favoring the forward reaction and increasing yield of products

  If Kc < 1, the proportion of products to reactants is lower, favoring the backwards reaction and decreasing yield of products. 

  The concentration of any solid is 1. 

  If K = 1, the proportion of products to reactants is the same, thus at equilibrium 
• Kc only changes when there is a temperature change.

  If a reaction is endothermic with an increase in temperature, then the Kc increases, as more product is made.

  If a reaction is exothermic with an increase in temperature, then the Kc decreases, as less product is made
• Increasing the concentration of reactant/product will cause disruption in the equilibrium system. According to LCP, the system will counteract this change by favouring

   the forward/backward reaction.
• An increase in pressure favours the reaction side that has less molecules.

  Increasing the pressure will cause a disruption in the equilibrium system. According to LCP, the system will counteract this change by favouring the reaction with fewer molecules. Thus, the position of equilibrium will shift to the left/right. 
• Increasing the temperature will favour the heat absorbing (endothermic) reaction. Decreasing the temperature will favour the heat releasing (exothermic) reaction 

  Increasing/decreasing the temperature will cause a disruption in the equilibrium system. According to LCP, the system will counteract this change by favouring the reaction that is endothermic/exothermic. Since the forward reaction is endothermic/exothermic, the equilibrium will shift to the left/right.
• Effect of Catalyst on Equilibrium 

  • No effect on the equilibrium system besides reducing the time taken for the equilibrium to be reached as it increases the rate of the forward and backwards reaction equally