Revise: EquilibriaFactors affecting equilibrium position
Reversible reactions in closed systems reach equilibrium where the rates of forward and reverse reactions are constant. Pressure, concentration and temperature all affect the equilibrium position.
Once equilibrium has been established, chemists can control certain reaction conditions to influence the position of the equilibrium.
Altering the reaction conditions can result in the yield of products increasing, and the process being more profitable.
Le Chatlelier’s principle states that if a system at equilibrium is subjected to any change, the system will adjust itself to counteract the applied change.
There are a number of factors that can be changed.
Concentration
Adding a chemical that is present on either side of the equation will cause a shift in the position of the equilibrium, as the system adjusts to counteract the change.
If hydrochloric acid was added to the equilibrium mixture, both hydrogen ions (H+) and chloride ions (Cl-) are being added.
Hydrogen ions are on the right hand side of the equilibrium, therefore the equilibrium will shift to the left hand side to compensate, resulting in a higher concentration of reactants.
Adding sodium hydroxide (NaOH) will also affect the position of the equilibrium.
While neither sodium ions (Na+) or hydroxide ions (OH-) are present on either side, the hydroxide ions will remove H+ ions and the equilibrium will shift to the right hand side to replace the hydrogen ions that were removed.
