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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

	Concentration	Coefficient
#	mol/L	integer
Aa
Bb
Cc
Dd

    

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OUTPUT   VARIABLES   &   GRAPHS

Variables	Values	Units
♦  Equilibrium constant, Keq
♦  Standard free energy change, ΔG°		J/mol

Chemical Equilibrium

Chemical equilibrium applies to reactions that can occur in both directions, such as:

     CH₄(g) + H₂O(g) <==> CO(g) + 3H₂(g);      AgBr(s) <==> Ag⁺(aq) + Br^-(aq);      HNO₂ <==> H⁺ + NO₂^-.

After some of the products are created, the products begin to react to form the reactants. The reactants are then constantly forming products and vice-versa.

Chemical equilibrium is the state in which the concentrations of the reactants and products have no net change over time. Usually, this state results when the forward chemical reactions proceed at the same rate as their reverse reactions.

For a reversible chemical reaction:

     aA + bB <==> cC + dD ,      {e.g. for N₂ + 3H₂ <==> 2NH₃, a=1, b=3, c=2, d=0}

the Equilbrium constant is given by the equation:

     K_eq = [C]^c[D]^d/([A]^a[B]^b)

There are some special cases of K_eq (e.g., K_a for the ionization constant of an acid, K_b for the ionization constant of a base, K_d for the dissociation constant).

Also, the free energy changes in the chemical reaction at equilibrium is given by:

     ΔG° = -RTln(K_eq)

where
     K_eq = equilibrium constant
     ΔG° = Gibbs standard free energy change
     [A] = concentration of reactant A
     a = stochiometric coefficient of reactant A
     [C] = concentration of reactant C
     c = stoichiometric coefficient of reactant C
     R = universal gas constant = 8.3145 J.K^-1.mol^-1
     T = Temperature in °K

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY

• Rosenberg JL & Epstein LM; College Chemistry, Schaum's Outlines Series; McGraw Hill, New York, 1997.