Le  Cha telier's  principle states that  if a  dynamic equilibrium  is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish equilibrium. If  a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change. 1. Effect of change in concentration If the concentration of a substance is changed, the equilibrium will  shift  to minimize the effect of that change. when the concentration of one of the substances in, a system at equilibrium is increased, then the equilibrium will shift so as to use up the substance added. Suppose at equilibrium one of the reactants is added, the equilibrium will shift in the direction that consumes reactants, i.e., the forward direction. The more of the reactants would be converted into products. On the other hand, if one of the products is added the equilibriu