C7H5O2- dissociates as:
C7H5O2- +H2O -----> C7H5O2H + OH-
1*10^-2 0 0
1*10^-2-x x x
Kb = [C7H5O2H][OH-]/[C7H5O2-]
Kb = x*x/(c-x)
Assuming x can be ignored as compared to c
So, above expression becomes
Kb = x*x/(c)
so, x = sqrt (Kb*c)
x = sqrt ((1.5*10^-10)*1*10^-2) = 1.225*10^-6
since c is much greater than x, our assumption is correct
so, x = 1.225*10^-6 M
So, [OH-] = x = 1.225*10^-6 M
use:
pOH = -log [OH-]
= -log (1.225*10^-6)
= 5.912
use:
PH = 14 - pOH
= 14 - 5.912
= 8.09
Answer: 8.09
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