Question

1)At 25 ^oC the solubility of silver iodide is 8.94 x 10^-9 mol/L. Calculate the value of K_sp at this temperature. Give your answer in scientific notation to 2 SIGNIFICANT FIGURES (even though this is strictly incorrect)

2)The K_sp of Al(OH)₃ is 1.0 x 10^-33. What is the solubility of Al(OH)₃ in 0.0000010 M Al(NO₃)₃? Give your answer using scientific notation and to 2 significant figures (i.e., one decimal place).

Answer 1

Q1

[AgI] = 8.94*10^-9 M

Ksp= [Ag+][I-]

[Ag+] = [AgI] = 8.94*10^-9 M

[I-] = [AgI] = 8.94*10^-9 M

then

Ksp = (8.94*10^-9)(8.94*10^-9) = 7.992*10^-17

2 sig fig --> 8.0*10^-17

Q2

Al(OH)3 <-> Al+3 + 3OH-

Ksp = [Al+3][OH-]^3

[Al+3] = [Al(NO3)3] = 0.0000010

10^-33 = (0.0000010 ) * (OH)^3

[OH-] = ((10^-33) / (0.0000010))^(1/3) = 10^-9 M

then

1 mol of Al(OH)3 = 3 mol of OH-

x mol of Al(OH)3 =  10^-9 M

x = 1/3*10^-9

x = 3.333*10^-10 mol of Al(OH)3(s) per liter -> 3.3*10^-10 M