Question

why might heating hydrates in a crucible to find the percentage of water in the hyrate not be appropriate for all hydates?

is it because some are flammable and water vapour might escape?

Answer 1

If you are trying to determine the percent water, you WANT the water vapor to escape. Some hydrates (either before or after driving out the water) may react with air (oxygen or nitrogen). And some hydrates don't lose all of their water of hydration at one temperature; that is, one mole of water may come off at 110 C and two more moles of water come off at 200 C. You can't control the temperature with a burner and crucible. Are there some hydrates that may react with the crucible?

Answer 2

aren't crucible made to not react with hydrates?

Answer 3

They will react with HF to form a gas. In fact, HF will eat a hole in the bottom of the xble.

Answer 4

thank you :)