A student mixes 4.17 g of iron(II) sulphate heptahydrate, FeSO₄· 7H₂O (278 g/mol), with 1.98 g of…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student mixes 4.17 g of iron(II) sulphate heptahydrate, (), with 1.98 g of ammonium sulphate, (), in dilute sulphuric acid, concentrates the solution and crystallises it. The light green crystals of Mohr's salt () weigh 4.70 g after drying. Find the amount of each reactant, the theoretical mass of Mohr's salt, and the percentage yield.
Need a reminder? The key ideaShow
. The theoretical mass is set by the limiting reagent. Aniline and acetic anhydride react 1 : 1 to acetanilide. Propanone, iodine and sodium hydroxide react 1 : 3 : 4 to iodoform ().
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. and . They are equimolar, so neither is in excess.
Step 2. The theoretical amount of Mohr's salt is , which is .
Step 3. .
Answer: , , and .
Check. The yield is below 100 %, as it must be. Some salt stays in the solution after crystallisation.
Discussion (0)
Log in to join the discussion.
Loading…