Potash alum is KAl(SO₄)₂· 12H₂O with a molar mass of 474.37 g/mol…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Potash alum is with a molar mass of . Take the molar mass of water as and of aluminium as . Find the percentage of water of crystallisation, the percentage of aluminium and the mass of alum that holds of aluminium.
Need a reminder? The key ideaShow
Faraday's law for aluminium: with . Energy in kilowatt hours is . Thermite: gives out for 2 mol of Al. A hydrate has its water in the molar mass.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Water. , so the percentage is .
Step 2. Aluminium. .
Step 3. Alum for of aluminium. .
Answer: water, aluminium, and of alum.
Check. The molar mass ratio gives the same answer.
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