A 7.90 g sample of pure potassium permanganate, with a molar mass of 158 g/mol, is heated until it…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A sample of pure potassium permanganate, with a molar mass of , is heated until it stops giving off gas: . Find the moles of permanganate, the mass of oxygen given off and the mass of solid left.
Need a reminder? The key ideaShow
Moles = mass in g divided by molar mass in g/mol, or concentration in mol/L times volume in litres. Take every mole ratio from the balanced equation, and follow the chain one step at a time.
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. Moles. .
Step 2. Oxygen. The ratio is , so of . The mass is .
Step 3. Residue. .
Answer: , and .
Check. The residue is of , , and of , . The sum is .
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