In: Chemistry
Why are these solved differently? i need an explanation not just a quick answer.
The Ksp of Al(OH)3 is 1.0 x 10-33. What is the solubility of Al(OH)3 in 0.00010 M Al(NO3)3? answer is (7.2x10^-11)
The Ksp of Al(OH)3 is 1.0 x 10-33. What is the solubility of Al(OH)3 in 0.000010 M NaOH? answer is (1.0x10^-18)
In the first case we have a aluminium nitrate Al(NO3)3 with aluminium hydroxide Al(OH)3 hence aluminium nitrate is highly soluble and dissociates completely in its ions. Finally we have a additional moles of Al3+ due to aluminium nitrate dissociation it means that in the Ksp equation we have to take total concentration of Al3+ and OH- .We also assume that 's' is the solubility of the ions and its is very small as compared to 0.00010M. After that equating all these values we have a solubility data.
In second part instead of nitrate we have strong base NaOH which dissociates into its ions i.e Na+ and OH- completely.Therefore overall we have additional hydroxide concentration along with hydroxide that are coming from aluminium hydroxide.Therefore in Ksp equation we have to take total concentration of OH- and Al3+ and solve the equation..we get solubility.