Question

calculate the theoretical yield for the production of alum using the following equation. 2 Al (s) + 2 KOH 22 H2O+4 H2So4 2 KAI(SO)212 H2O (s) +3 H2 (g) In Part 2 of this experiment you will qualitatively analyze the composition of alum, KAI(SO4)2-12 H2O (s), by analyzing for AB+, s042-, K+, and H2O. o When 0.1 M BaCl2 is added to an aqueous solution of alum, what reaction produces a precipitate? Write the net ionic equation for the reaction. Use the solubility table in ppendix 1 to help you determine what precipitate is formed By adding 0.1 M KOH to an aqueous solution of alum, what ion are you analyzing for? Why must you add the KOH drop by drop? What reaction occurs when excess KOH is dded? w wul you analyze for the presence of H20 in alum? flame test done using an aqueous KCI solution as well as an aqueous alum solution? experiment, you will be using concentrated 9 M H,504 What ions in alum are you analyzing for in the flame test, Al3+, so42, or K+? Why is In this experiment, you will be using concentrated 9 M H2SO4

What is the net ionic equation adding KOH drop by drop and what is the equation when you add too much?

Answer 1

Dear student

Potassium alum is a hydrated double salt of potassium sulphate and aluminium sulphate - K2SO4.Al2(SO4)3.24H2O. An aqueous solution of it contains K(+), Al(3+) and larger amount of SO4(2-) ions.

On adding potassium hydroxide, initially, a white precipitate of aluminium hydroxide will be formed by the reaction between the aluminium and hydroxide ions.

Al2SO4 (aq) + 6KOH (aq) = 2Al(OH)3 (s) + 3Na2SO4 (aq)

But if KOH is added in excess, the aluminium hydroxide so formed will dissolve to give a clear, colourless solution by forming the complex ion [Al(OH)4]-.

Al(OH)3 (s) + KOH (aq) = K[Al(OH)4] (aq)

Potassium sulphate does not react with KOH in any meaningful fashion.

So, the addition of Potassium hydroxide in excess will result in a colourless solution having K(+), SO4(2-) and [Al(OH)4](-) ions. But, the use of a limited amount of the alkali will result in the separation of aluminium as insoluble aluminium hydroxide from the solution