Chemical equilibrium Flashcards
When is chemical equilibrium reached?
When the concentration of reactants and products is constant, and the rates of the forward and reverse reactions are equal.
Equilibrium constant (K) -
Characterises the composition of the reaction mixture.
For general reaction equation aA +bB<=> cC + dD
What is the k equation.
K = [C]^c[D]^d/[A]^a[B]^b
Where A,B,C,D are the equilibrium concentrations and a,b,c,d are the stoichiometric coefficients.
What does K equation indicate
Position of equilibrium
What to do for K equation question when equilibrium is not formed at the start.
We see value of concentration of products produced at equilibrium and using mole rules rake that away from initial concentration of reactants and insert new values into K equation.
Unit of equilibrium constant, K
No unit
Concentration of pure solids or pure liquids at equilibrium
1
Numerical value of equilibrium constant depends on what?
Depends on temperature and is independent of pressure and concentration.
For endothermic reactions what does an increase in temperature cause?
An increase in K value and increased yield of product produced. Since forward reaction is favoured.
For exothermic reaction what does an increase in temperature cause?
A decrease in K value and a decrease in yield of product produced since reverse reaction is favoured.
What does the presence of a catalyst do to the value of the equilibrium constant, K
Nothing
Water equilibrium
Equilibrium between water and hydronium and hydroxide ions.
2H20(l)<=> H30+(aq) + OH-(aq)
