Hello. I am a pharmacy student at a university in the Philippines. For our inorganic chemistry laboratory, we were asked to synthesize alum. These were the following chemicals used:

For NH₄ Alum:
Diluted Ammonia solution
Diluted Sulfuric Acid
Aluminum Sulfate

For Potassium Alum:
Diluted Sulfuric Acid
Aluminum Sulfate
Potassium Sulfate

I was wondering if anyone knows the complete balanced chemical formula of these reactions? I seriously do not know how to approach this situation. Complex ions were never discussed in our class and I'm stumped and I really wish someone can help me.

Well, all I got is this:

For Ammonium Alum
2NH₃⁺ + H₂SO₄  (NH₄)₂SO₄ //// Al₂₍SO₄)₃ + (NH₄)₂SO₄  2 (NH₄)Al(SO₄)₂

For Potassium Alum:
H₂SO₄ + K₂SO₄ + Al₂(SO₄)₃  KAl(SO₄)₂ + (I do not know what to put here :/)

Well, I need a balanced chemical equation to determine the theoretical yield. How do I know the number of moles of Potassium alum? Do I just assume it to be 2?

I'll just lay it out there:

0.5 mL was added to 50 mL distilled water. Mixture was heated to boiling, then 1.25 g of Aluminum Sulfate and 3.5 g of Potassium Sulfate was dissolved in it. The solution was filtered and cooled to allow crystallization.

I wasn't sure what mass you were asking, so I listed all except the actual yield, which I presume is not important for determining theoretical yield...?

I'll just lay it out there:

0.5 mL was added to 50 mL distilled water. Mixture was heated to boiling, then 1.25 g of Aluminum Sulfate and 3.5 g of Potassium Sulfate was dissolved in it. The solution was filtered and cooled to allow crystallization.

This is a good first step.  You have grams, you can convert to moles, and using a balanced chemical reaction, you can determine how much you should get, in terms of moles and also mass.

I wasn't sure what mass you were asking, so I listed all except the actual yield, which I presume is not important for determining theoretical yield...?

No, you don't need actual yield to determine theoretical yield.  But you do need it for percent yield, if that question comes up later.

Well then, answer my first question.What atoms are left after the formation of the alum double salt?  Can you account for them, as stable compounds?  Then, can you balance the reaction?

I'm sorry to answer a question with a question, but that's what we do here.  Its all the the Forum Rules{click}, you agreed to read them and follow them when you registered for this board.  You can use the symbols above to make chemical equations easier for us to follow.

Well, the only atom left is the H⁺ atom, so I kinda thought that H₂SO₄ is a byproduct of the reaction..?

Beware that you have H₂SO₄ in your reactant side. Typically the same chemical will not appear on both sides of a chemical equation but you can try to cancel out them.

I can't say H⁺ because there is no evolution of gas, right?

No. Have H⁺ doesn't mean having H₂.