Which one of the following salts, when dissolved in water, produces the solution with the lowest pH?

Question

a. KI

# b. NaI

# c. MgI2

# d. AlI3

I believe it's D since it gives highest number of I (Iodide) than the others.

Answer 1

they are asking which of these will under go the greatest hydrolysis.

which will split the most water molecules , keeping the most OH- ions tied up in a hydroxide precipitate, releasing from water thus the most H+ ions

a. KI will not spilt water, KOH will not hold OH- ions, it is a strong base

b. NaI will not spilt water, NaOH will not hold OH- ions, it is a strong base

c. MgI2 will react with water: MgI2 & H2O --> Mg(OH)2 (s) & 2H+  & 2 I-

the Ksp for Mg(OH)2 is 1.6e-12

d. AlI3  will react with water: AlI3 & H2O --> Al(OH)3 (s) & 3H+  & 3 I-

the Ksp for Al(OH)3 is about 1.9 x 10-33

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the K of Al(OH)3 shows it to be more stable, that's the one that will react with water & release more H+ ions

I also believe that "D" is the right answer