(a) Will Co(OH)2 precipitate from solution if the pH of a 0.042 M solution of Co

Question

(a) Will Co(OH)2 precipitate from solution if the pH of a 0.042 M solution of Co(NO3)2 is adjusted to 7.95? (Ksp of Co(OH)2 is 1.3×10-15). Support your answer by calculating the ion product (Q) of the Co(OH)2 solution. (a) Will Co(OH)2 precipitate from solution if the pH of a 0.042 M solution of Co(NO3)2 is adjusted to 7.95? (Ksp of Co(OH)2 is 1.3×10-15). Support your answer by calculating the ion product (Q) of the Co(OH)2 solution. (a) Will Co(OH)2 precipitate from solution if the pH of a 0.042 M solution of Co(NO3)2 is adjusted to 7.95? (Ksp of Co(OH)2 is 1.3×10-15). Support your answer by calculating the ion product (Q) of the Co(OH)2 solution.

Explanation / Answer

pH = 7.95

So pOH = 14-7.95 = 6.05

-log [OH] = 6.05

log 1/[OH] = 6.05

hydroxide ion concentration = 8.9*10 -7

concentration of Co ion= 0.042 M

concentration of hydroxide ion = [8.9*10 -7] -2

  so ionic  product of Co(OH)2=     0.042*[8.9*10 -7] -2       

                                                 =3.32682* 10 -14 which is more than given solubilty product value

so cobalt hydroxide will precipitate from the above pH adjustment.

NOTE -------------------------------- Co(OH)2.---------------------------> Co 2+ +   2[OH] -1

                               

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