Problems making Calcium hydroxide from Calcium chloride and Sodium hydroxide

[harald25]

Hey!
I've been trying to find calcium hydroxide where I live to no avail.
I can only purchase it in 20kg batches which is way more than I need.
So, I decided to see if I could make it myself.

I've been able to get a hold of calcium chloride and sodium hydroxide and I've figured that the reaction will be like this:
CaCl2 (aq) + 2NaOH(aq) = Ca(OH)2(s) + 2NaCl(aq)

I have been asking around on a different forum and I was told there to do the following:
1) Dissolve 88g NaOH in 100ml of water
2) Dissolve 110g CaCl2 in 200ml of water
3) Mix the two solutions
I was then told that out of this mixture Ca(OH)2 would precipitate as a fine milky white powder.

So... I tried! But after mixing the two solutions what I was left with was a thick gray slush that nothing could possibly precipitate out of.
I mixed in quite a lot of extra water in an attempt to dilute it enough that precipitation would occur, but I couldn't really get it to happen.

Is there anyone here who can give me some tips?
I really want to understand this as chemistry is something that really fascinates me!

Also, another question.
Before I did this I wanted to know how much heat the reaction would generate, but I couldn't figure out how.
I tried using the standard formation enthalpies and then subtracting the sum of the reactants from the sum of the products. But this resulted in a positive enthalpy which would mean an endothermic reaction, and that is definitely not right!

So, again. I would really appreciate some help! =)

 

[Infundibulum]

Hi,

Are you sure you have the right and fairly clean reagents? The reaction between calcium chloride and sodium hydroxide is almost instant and produces a milky-white calcium hydroxide precipitate almost immediately....at least the last time I tried it.

 

[harald25]

Blah!
I feel like a complete noob now
The NaOH is pure.
But the CaCl2 was not. I checked the back of the package and there it only said calcium chloride.
But now that I checked the material safety data sheet I see that there is also activated carbon in it.

So that explains it I guess!
I'd still like to know how to calculate the heat generated by the reaction though!