Chemical equilibria

• When a system at equilibrium experiences a change, the equilibrium shifts in the direction that reduces the magnitude of change.
• If more product is formed, then K increases; if less product is formed, then K decreases.
• The equilibrium constant (K) is the ratio of products to reactants at equilibrium.
• Activities of any species and it’s concentration are associated with a multiplier called the activity coefficient
• Activity coefficient=[species concentration]* ionic strength of a specie
• Ionic Strength=1/2 * sum(concentration*z^2)
• In general, the larger the charge on an ion, the greater its activity coefficient will be.
• Thermodynamic constant is a constant that is not affected by the absence of a electrolyte or a very low electrolyte concentration
• In neutral equilibrium species the equilibrium is largely independent of the electrolyte concentration
• Effect of an electrolyte added to the medium on the equilibrium depends on ionic strength
• solutions with an ionic strength of 0,1M or less equilibrium is independent of a type of ions but dependent on ionic strength .

  But if this solution is more than 0,1 M bein independent of electrolyte types is invalid
• ActiviTy of an X species = Ax= [X concentration] * activity coefficient of X
• Dilute solutions with least ionic strength, the activity coefficient is equal to 1.

  Ionic strength increases,the activity coefficient decreases
• • Activity coefficient of species with not concentrated solutions depends only on ionic strength of the solution
• Activity coefficients of ions with same charge in solution are approximately equal to each other
• The activity of uncharged molecule is approximately 1
• In diluted solutions ,activity coefficient of cations and anions can be considered as 1.
• Activity coefficient of X = (0,51*Zx2*ionic strength 1/2) /( 1+(3,3.ax)*ionic strength1/2)

  ax= effective diameter