Question

# A 75 L solution of 0.63 M Fe(NO3)3 is mixed with 89 mL of 0.33 M...

A 75 L solution of 0.63 M Fe(NO3)3 is mixed with 89 mL of 0.33 M Ni(NO3)2. Ksp Fe(OH)3=1.63x10^-39 and Ksp Ni(OH)2 = 6x10^-16

(a) If solid KOH is added to the solution, what will precipitate first? Give the chemical formula.

(b) If solid KOH is added to the solution, at what concentration of [OH-] will one begin to see the first sign of precipitate?

(c) At what concentration of [OH-] will one begin to see the first sign of precipitation of the second complex?

(d) What is the chemical formula for this second substance precipitating?

a. If solid KOH is added to a mixture of 75 L of 0.63M of Fe(NO3)3 and 85 mL of 0.33M of Ni(NO3)2, then, Fe(OH)3 will precipitate out first as it is more saturated.

b. The concentration of [OH-] at which the first precipitate occurs

1.63 x 10-39 = X x 0.63 M

X = 2.587 x 10-39 M

c. The concentration of [OH-] at which the second precipitation occurs

6 x 10-16 = X x 0.33M

X = 18.18 x 10-16 M

d. Chemical formula for second substance precipitating is Ni(OH)2.

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