Question

Chemistry help? :(

If the mass of a crucible + hydrate was 20.000 grams, and the mass of the empty crucible was 5.000 grams. What is the percent water in this hydrate if the crucible and hydrate were heated until all the water of the hydration was driven off and the mass of the crucible and anhydrate were 10.000 grams?

Answer 1

Sounds like a pre- or post-lab question. What are you trying isolate? :)

Hydrates are hydrated salts of various compounds: they consist of water molecules in certain ratios to form the crystal.

I feel like dissolving the hydrate in water and evaporating the water would be cleaner than trying to heat the hydrate to evaporate the water that is in the solid.

So what you presumably did (or will do, or were supposed to do if you skipped lab...) was isolate the anhydrate of the salt.

You started with `15.000g` of salt, and after evaporating were left with `5.000g`: there must have been a lot of water in that salt!

The issue is if you don't give me the salt I can't give you a very precise answer. But doing some crude math,

`(15-5)/(5) * 100% = 200%`

is the percent water in that salt.