In: Chemistry
Sodium benzoate NaC6H5CO2, kb = 6.3×10^-5. is iften
used as a preservative in food products if it is added water to
bring the concentartaion to .10M. the benzoate ion, C6H5CO^-2
reacts with water according to the following equiliburium:
C6H5CO^-2 + H2O ➡ C6 H5 CO2 +OH^-1 Kb= 6.3×10^-5
a. write the equibulirum expression for the reactions.
b. complete an ICE table using the initial concentration of .10 M venzoate ion.
c. determined what equibulirum concentration of (C6H5CO2^-1), ( C6H5CO2H) and (OH^-1).
d. determined the Delta G for the reaction.
C6H5COO- + H2O --------------> C6 H5 CO2H + OH- Kb= 6.3×10^-5
a)
equilibrium expression = [C6 H5 CO2H] [OH-] / [C6H5COO-]
b)
C6H5COO- + H2O --------------> C6 H5 CO2H + OH-
0.10 0 0 -----------> I
-x + x + x ------------> C
0.10-x x x ------------> E
c)
Kc = [C6 H5 CO2H] [OH-] / [C6H5COO-]
Kb = x^2 / 0.1 - x
6.3×10^-5 = x^2 / 0.1 - x
x = 2.48 x 10^-3
[[C6 H5 CO2H] = 2.48 x 10^-3 M
[OH-] = 2.48 x 10^-3 M
[C6 H5 CO2-] = 0.0975 M
d)
delta G = - RT ln K
= - 8.314 x 10^-3 x 298 x ln (6.3 x 10^-5)
= 23.96 kJ/mol