II. General Solution to Equilibria Problems | ||||
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II-1. Introduction | II-2. Equilibrium Constant | II-3. Le Chatelier's Principle | II-4. Reaction Quotient | II-5. General Solution |
The expression for the reaction quotient, Q, is the same as the expression for the equilibrium constant (see II-2.), but for partial pressures or concentrations of the reactants and products before the system reaches equilibrium.
If Q < K then the reaction is proceeding in the forward direction.
If Q > K then the reaction is proceeding in the reverse direction.
Example:
N_{2}O_{4 (g)} 2 NO_{2 (g)} K_{eq} = 11 atm (T = 373 K)
mix 0.2 mol of N_{2}O_{4} with 0.2 mol of NO_{2} in a 4.0 L flask at 100^{o}C.
Q = (P_{NO2})^{2} / P_{N2O4}
First find P_{NO2} and P_{N2O4} using PV = nRT
P_{NO2} = P_{N2O4} = (0.20 mol)(0.0821 L atm/mol K)(373 K)/(4.0 L) = 1.5 atm
Q = (1.5 atm)^{2}/1.5 atm = 1.5 atm
Q < K, so the reaction will proceed in the forward direction, N_{2}O_{4 (g)} 2 NO_{2 (g)} until it reaches equilibrium.
Equilibrium Practice Problems | |
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