Lithium aluminium hydride is made by 4LiH + AlCl₃ → LiAlH₄ + 3LiCl…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Lithium aluminium hydride is made by . A chemist starts with of lithium hydride () and enough aluminium chloride (). Take for LiAlH. Find the mass of lithium aluminium hydride, the mass of aluminium chloride needed, and the volume of hydrogen at and that the hydride gives with water. Take .
Need a reminder? The key ideaShow
Each Cl of a chloride that is hydrolysed ends as one HCl, and HCl is a strong acid, so equals the moles of HCl for each litre. A gas at and has a molar volume of . Magnesium silicide and acid give silane, . Lithium aluminium hydride and water give four moles of hydrogen for each mole.
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 of LiH. .
Step 2. The hydride. One quarter as many moles: , which weighs .
Step 3. Aluminium chloride. One mole for each mole of the hydride: .
Step 4. Hydrogen. , which is .
Answer: , and .
Check. All four hydrogen atoms of the hydride come out as hydrogen gas, and none of the hydrogen of the water does, apart from the four needed for the hydroxide.
Discussion (0)
Log in to join the discussion.
Loading…