# How to prepare the electrolyte solution. Using stoichiometric analysis.



## eduardo.met (Apr 2, 2022)

I considered some operational variables of a Moebius cell.
* Electrolytic solution: 40-100 g Ag/L, In my case I used 93.3g of pure Ag.
* Free HNO3: 8-12% ----Only use 10% free acid.
The electrolyte is made up of AgNO3 in solution. So let's consider the following equation: *3Ag(s) + 4HNO3 --> 3AgNO3 + NO + 2H2O*


=> 72.66 g HNO3; But this is considering the nitric acid is 100% Pure. In most cases nitric acid is 65%
If [HNO] = 65% and density of nitric acid is 1.51g/cm3
Thus: 


Density = m/v ====> therefore v= m/density


*V= 74.17cm3* ; Therefore, the exact amount of nitric acid required to react with silver is 74.17 ml.

*Here the preparation:*
We put the silver in a beaker in which we pour the amount of nitric acid that we calculated. To speed up the reaction we need to heat it.
Little by little, the nitric acid will be consumed and silver nitrate crystals (AgNO3) will form. Then; Once all the silver has been converted into nitrate stop heating the beaker, we are going to add a little distilled water so that the crystals dissolve. Once dissolved, we calculate the free nitric acid we need.
=> 10%(74.17)= 7 ml nitric acid.
We add the free nitric acid and finally add distilled water up to 1 liter.

I tried to make it as simple as possible so that it can be understandable. The stoichiometric analysis allows us to be somewhat more rigorous in terms of the materials or reagents to be used; even more when we use large amounts.
In practice there is a close to 1:1 ratio of Ag and HNO3.
Kind regards.

Eduardo.


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## goldandsilver123 (Apr 2, 2022)

My experience is that nitric acid reduces to NO only in dilute HNO3 solutions.

Most of the reaction is HNO3 -> NO2


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## eduardo.met (Apr 2, 2022)

Perhaps it could be in the presence of other elements. I think the equations should be analyzed.


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## orvi (Apr 3, 2022)

I have experienced deeper reduction of nitric, when dissolving silver. It was clearly visible, that gas escaping the vessel isn´t pure NO2 - due to it´s very light brown colour. In my opinion, it was mixture of NO/NO2. 

Consumption of the acid is very dependent on conditions. As it was said, if you don´t overheat the solution, reduction will be deeper. With silver it is quite impractical to work with lower temperatures tho.

My experiments shown the consumption to be somewhere in the range of 105+ml for 100g silver (65% nitric). In majority of cases more than 115 ml/100g.


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