When 0.277 mol of C4H9COOH is dissolved in 0.963 L of water, proton transfer occurs.
C4H9COOH + H2O ⇄C4H9COO- + H3O+
The equilibrium concentration of H3O+ ions is 0.00212 M. Evaluate Keq.
Let us write the reaction as
C4H9COOH + H2O <-------------> C4H9COO- + H3O+
0.277 55.5 0 0 initial moles
0.277 -x 55.5-x x x after reaction at equilibrium
Given at equilibrium [H+] = x = 0.00212 M
thus moles of H+ in solution = molarity x volume
= 0.00212 x 0.963
=0.00204 moles
Thus
C4H9COOH + H2O <-------------> C4H9COO- + H3O+
0.277 55.5 0 0 initial moles
0.277 -x 55.5-x x x after reaction at equilibrium
0.277-0.00204 55.5-0.00204 0.00204 0.00204 moles at equilibrium
0.275/0.963 55.497/0.963 0.00204/0.963 0.00204/0.963 equilibrium concentrations
thus Keq = [C4H9COO-][H3O+]/ [C4H9COOH][H2O]
= 0.00204 x0.00204 /0.275 x 55.497
= 2.72 x10-7
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