Question
Aluminum hydroxide reacts with an excess of hydroxide ions to form the complex ion Al(OH)4-
a)Write an equation for this reaction
b) Calculate K.
c) Determine the solubility of Al(OH)3 in (mol/L) at pH 12.0
My equation was
Al(OH)3 + OH- --> Al(OH)4-
but I'm wondering if I may need to balance out the OH- with H+?
Also, I'm a little confused on what K is. I know it's an equilibrium constant, but how does it differ from Ksp or Kc or Kp? Do you have to decide which constant you're looking for? And how do I find this once I determine the right constant?
Your equation is correct for the formation of Al(OH)4^-. There is nothing to balance out; i.e., atoms balance, charge balances, so nothing needs to be added.
The formation constant is just another equilibrium constant but it pertains to the formation of complex ions; therefore, they have given the name of formation constant to it just as they gave solubility constant to the solubility of ppts. The K expression is the same as all the others; that is, (products)/(reactants) with each raised to a power indicated by the coefficient.
I don't know how to calculate K with "nothing" given.
If you find K, however, then
K = [(Al(OH)4^-)/(OH^-)]
Plug in OH^- and knowing K calculate (Al(OH)4^-.
I made a typo above.
....to it just as they gave solubility constant...... should read
....to it just as they gave solubility PRODUCT constant.......
a)Write an equation for this reaction
b) Calculate K.
c) Determine the solubility of Al(OH)3 in (mol/L) at pH 12.0
My equation was
Al(OH)3 + OH- --> Al(OH)4-
but I'm wondering if I may need to balance out the OH- with H+?
Also, I'm a little confused on what K is. I know it's an equilibrium constant, but how does it differ from Ksp or Kc or Kp? Do you have to decide which constant you're looking for? And how do I find this once I determine the right constant?
Your equation is correct for the formation of Al(OH)4^-. There is nothing to balance out; i.e., atoms balance, charge balances, so nothing needs to be added.
The formation constant is just another equilibrium constant but it pertains to the formation of complex ions; therefore, they have given the name of formation constant to it just as they gave solubility constant to the solubility of ppts. The K expression is the same as all the others; that is, (products)/(reactants) with each raised to a power indicated by the coefficient.
I don't know how to calculate K with "nothing" given.
If you find K, however, then
K = [(Al(OH)4^-)/(OH^-)]
Plug in OH^- and knowing K calculate (Al(OH)4^-.
I made a typo above.
....to it just as they gave solubility constant...... should read
....to it just as they gave solubility PRODUCT constant.......