Quick Chemistry Question

HemlockGrey · Post by **HemlockGrey** » 2005-09-15 08:47pm

Having been failed in succession by my textbook, Google, and Wikipedia (in that order), I now turn to you folks...can you name me 2 hydrated salts that decompose in heat?

Admiral Valdemar · Post by **Admiral Valdemar** » 2005-09-15 09:43pm

How much heat? I don't think any hydrated salt is completely stable as to withstand infinite thermal tolerance, so a band of temperature would be nice.

I believe magnesium sulphate would be one you could mention since it can be heated to breakdown and measure water content.

HemlockGrey · Post by **HemlockGrey** » 2005-09-15 09:47pm

The question is rather vague; it doesn't give a range of heat. I'm not sure what the point of it was but it was the last question on my AP Chem lab so I needed an answer.

Thanks for magnesium sulFATE (

), and I remembered something about ammonia salts decomposing in heat...

tharkûn · Post by **tharkûn** » 2005-09-16 01:32am

All of them decompose if you heat them hot enough.

I'd go with include sodium carbonate decahydrate and magnesium sulfate heptahydrate already listed as these have nice stoichiometric hydration. Other fun ones include cadmium carbonate, sodium tetraborate (borax), cupric sulfate, ferric sulphate, cupric orthodtungstate for which I don't recall the amount of hydration (for some it veries for cadmium it is 2.something).

Molyneux · Post by **Molyneux** » 2005-09-16 09:02pm

tharkûn wrote:All of them decompose if you heat them hot enough.

I'd go with include sodium carbonate decahydrate and magnesium sulfate heptahydrate already listed as these have nice stoichiometric hydration. Other fun ones include cadmium carbonate, sodium tetraborate (borax), cupric sulfate, ferric sulphate, cupric orthodtungstate for which I don't recall the amount of hydration (for some it veries for cadmium it is 2.something).

We worked with copper(II) sulfate in th'summer chem course I took recently! Only had to heat it with a Bunsen burner to get it to decompose after about 5 minutes...that's, what, a few hundred degrees tops?

Admiral Valdemar · Post by **Admiral Valdemar** » 2005-09-17 10:34am

Assuming the Bunsen was on fierce flame, then yeah, around 800 degrees centigrade I believe at peak. This question is rather vague though, you could simply name any salt and be done with it. Lazy teacher I reckon.