Equilibrium Question 912
Question: What is the minimum pH when $ Fe{{(OH)}_3}, $ starts precipitating from a solution containing $ 0.1MFeCl_3 $ - $ k _{sp} $ of $ Fe{{(OH)} _3}=8\times {10^{-13}}M^{3}(\log 2=0.3) $
Options:
A) 3.7
B) 5.7
C) 10.3
D) 8.3
Show Answer
Answer:
Correct Answer: C
Solution:
$ 8\times {10^{-13}}=[F{e^{3+}}]{{[O-H]}^{3}} $
$ [O{H^{-}}]=2\times {10^{-4}} $
$ pOH=4-\log 2=3.7 $
$ pH=10.3 $
