Sciencemadness Discussion Board

How to push this reaction to the right ?

Sulaiman - 2-8-2016 at 08:13

I bought calcium nitrate with the intention of making nitric acid using drain cleaner sulphuric acid,
the byproduct, calcium sulphate is no use to me, so I am considering HCl in the form of brick cleaner;

Ca(NO3)2 + 2HCl = CaCl2 + 2HNO3


How can I determine the equilibrium, and move it to the right ?

by Le Châtelier's principle, excess HCl would help
but I would expect recovery of products to be problematic,
is this possible, and practical?

Velzee - 2-8-2016 at 08:58

According to my notes;

The Equilibrium Constant(K)=(molarity of the products)/(molarity of the reactants)

And you've already know the first rule of Le Châtelier's Principle:

Rule #1—If you increase the amount of reactants, the amount of products shall also increase.

And:

Rule #2—Remove the products to get more of the products.

The way I'd suggest is to boil the solution to recover the HNO3, but this probably will be heavily contaminated with HCl. This will be a messy reaction, indeed and probably not worth it. I suggest you use H2SO4 instead, as this would precipitate CaSO4 and leave HNO3 in the solution, but this would leave quite a messy clean up in the reaction flask, but definitely a purer product if you distill the HNO3.

Ca(NO3)2 + H2SO4 ---> CaSO4 + 2HNO3



[Edited on 8/2/2016 by Velzee]

[Edited on 8/2/2016 by Velzee]

DraconicAcid - 2-8-2016 at 09:13

Quote: Originally posted by Velzee  

If you choose your proposed method, I believe you should increase the temperature and boil the solution to shift the equilibrium to the right.

That won't work, because HCl is more volatile than HNO3.

zwt - 2-8-2016 at 09:17

Both nitric and hydrochloric acid form azeotropes, and the hydrochloric acid azeotrope has a lower boiling point. Distilling a mixture of calcium nitrate and concentrated hydrochloric acid will first yield wet hydrogen chloride gas, then azeotropic hydrochloric acid, possibly contaminated with side products like nitrosyl chloride and, yes, traces of nitric acid.

You could add copper to your nitrate and hydrochloric acid mix, à la NurdRage, but the reaction is very inefficient, the acid produced heavily contaminated, and the calcium chloride byproduct contaminated with copper and residual nitrate.

Alternatively, if sodium carbonate is cheaply available, you could make your nitric acid with sulfuric acid and calcium nitrate, boil the sulfate byproduct with sodium carbonate solution to yield calcium carbonate and sodium sulfate, and react the calcium carbonate with hydrochloric acid to give the desired calcium chloride.

[Edited on 2-8-2016 by zwt]

Velzee - 2-8-2016 at 09:23

Quote: Originally posted by DraconicAcid  
Quote: Originally posted by Velzee  

If you choose your proposed method, I believe you should increase the temperature and boil the solution to shift the equilibrium to the right.

That won't work, because HCl is more volatile than HNO3.


Ah, okay, I edited my post to remove my error.

Richard3050 - 2-8-2016 at 09:58

I would also highly recommend using sulfuric acid. Even if the calcium chloride product is more interesting then the calcium sulfate it's much easier to do. If you look online for videos about nitric acid synthesis almost always sulfuric is used. The boiling point of sulfuric is so much higher than nitric that boiling the mixture will automatically push the reaction to the right and give you a nearly pure product. Check out a video by NileRed on YouTube to use as an example.

PHILOU Zrealone - 2-8-2016 at 10:03

1°) HCl is much stonger acid than HNO3, but is also more volatile.

2°) CaCl2 is quite soluble into water just like Ca(NO3)2 so precipitation is no help here to displace equilibrium.

3°) Traces HCl or CaCl2 with HNO3 arround will gas out O=N-Cl (nitrosyl chloride) and be a kind of aqua regia.

Thus not practical!

blogfast25 - 2-8-2016 at 10:04

Quote: Originally posted by Richard3050  
The boiling point of sulfuric is so much higher than nitric that boiling the mixture will automatically push the reaction to the right and give you a nearly pure product. Check out a video by NileRed on YouTube to use as an example.


That's largely irrelevant here. CaSO4 is poorly soluble, so that pushes the reaction to near completion. Then filter of the CaSO4 hydrate and distil the filtrate.

Sulaiman - 2-8-2016 at 10:47

OK ... looks like the HCl option is not viable,
not a big surprise but I thought i'd ask anyway ... thanks.
H2SO4 + Ca(NO3)2 it will be.

unionised - 2-8-2016 at 11:42

Wow!
Nobody noticed?
HCl is a reducing agent; nitric acid is an oxidising agent and yet nobody saw the competing reaction as an possible issue?

HNO3 (aq) + 3 HCl (aq) → NOCl (g) + Cl2 (g) + 2 H2O (l)
et seq

PHILOU Zrealone - 2-8-2016 at 12:38

Quote: Originally posted by unionised  
Wow!
Nobody noticed?
HCl is a reducing agent; nitric acid is an oxidising agent and yet nobody saw the competing reaction as an possible issue?

HNO3 (aq) + 3 HCl (aq) → NOCl (g) + Cl2 (g) + 2 H2O (l)
et seq

You must be tired... :P;):)
Read 1rst § of ZWT's post and the 3°) of my post above this post.

unionised - 2-8-2016 at 12:45

Quote: Originally posted by PHILOU Zrealone  
Quote: Originally posted by unionised  
Wow!
Nobody noticed?
HCl is a reducing agent; nitric acid is an oxidising agent and yet nobody saw the competing reaction as an possible issue?

HNO3 (aq) + 3 HCl (aq) → NOCl (g) + Cl2 (g) + 2 H2O (l)
et seq

You must be tired... :P;):)
Read 1rst § of ZWT's post and the 3°) of my post above this post.


Yep; bed time.
However my point was that, under any circumstances where HNO3 might hope to be a meaningful product, decomposition as going to be a major problem. In a "never mind traces- this won't work" sort of way.

Magpie - 2-8-2016 at 13:16

I would recommend filtering off that CaSO4 before distilling. The presence of all those solids might lead to some heavy bumping.

Use of a filter aid like diatomaceous earth (celite, etc) will help in the filtration of the slimey CaSO4.

magpie

Sulaiman - 2-8-2016 at 16:53

so are you in effect saying that the reaction Ca(NO3)2 + H2SO4 => CaSO4 + 2HNO3
will run to the right without having to boill off the HNO3 ?
I'd prefer doing the reaction in a beaker, filtering and distilling
to having to get the calcium sulphate out of my one and only 500ml 24/28 flask.
(which is another reason I was considering HCl)

Magpie - 2-8-2016 at 18:43

Quote: Originally posted by Sulaiman  
so are you in effect saying that the reaction Ca(NO3)2 + H2SO4 => CaSO4 + 2HNO3
will run to the right without having to boill off the HNO3 ?


Yes. When a precipitate is formed the reactants are taken out of the solution, driving it to the right. This is similar to generating a gas where it escapes the reactor thus driving the reaction to the right.

I have never made HNO3 with Ca(NO3)2 but have made it several times with KNO3 and sulfuric acid per my procedure in prepublication. I don't see where this will be much different except you will have to deal with that messy CaSO4.

blogfast25 - 2-8-2016 at 18:43

Quote: Originally posted by Sulaiman  
so are you in effect saying that the reaction Ca(NO3)2 + H2SO4 => CaSO4 + 2HNO3
will run to the right without having to boill off the HNO3 ?
I'd prefer doing the reaction in a beaker, filtering and distilling
to having to get the calcium sulphate out of my one and only 500ml 24/28 flask.
(which is another reason I was considering HCl)


Just rewrite the equation:

Ca(NO3)2(aq) + H2SO4(aq) => CaSO4(s) + 2HNO3(aq)

Clear now? Filter off the solids and you have an (impure) solution of HNO3. Distil and be damned. :)

[Edited on 3-8-2016 by blogfast25]

Magpie - 2-8-2016 at 19:47

I think it would be useful to take a look at my procedure for making phosphoric acid in prepublication. Note the voluminous amount of CaSO4 generated and my comments about having enough water present.

Don't worry having too much water in the product distillate. You can always distill to the azeotrope (67% IIRC) and even to fuming nitric if that is what you ultimately want.