[CopperSmurf]

Hi. Me and a few people here have different ideas about this.peoblem.
Basically it is a redox reaction between Cu²⁺ and S⁴⁺.
2Cu²⁺ + S⁴⁺ --> 2Cu⁺ + S⁶⁺
We got a balanced reaction equation:
2CuSO₄.5H₂O + 4NaCl + NaHSO₃ + NaOH ----> 2CuCl + 3Na₂SO₄ + 2HCl + 10H₂O.

Afterwards, we are going to use that Copper (I) chloride salt in a Sandmeyer reaction ( 1:1 ratio between the Cu and the aryl amine after making the amine into an ionic compound by adding HCl and adding 0.106 moles of sodium nitrite to make the N₂⁺ for the Sandmeyer ). We're going to put the chloride onto the organic compound.

We will be using 0.124 moles of copper (II) sulfate pentahydrate, 0.171 moles NaCl, 0.0692 moles of NaHSO₃, 0.118 moles NaOH and 0.102 moles of the aryl amine. All of these are solids, except the aryl amine, and eventually dissolved in water.

So our problem is, some of us believe that the NaCl is the limiting reagent if we strictly took the number of moles and divided by the coefficient in the equation, and others (including me) believes that the CuSO₄.5H₂O is the limiting reagent because it is being used in the redox.

To me, it doesn't make sense to say that the NaCl is the limiting reagent! But does it make sense that NaCl is the limiting reagent to you in this case or is there something wrong in our reaction equation?

[Borek]

Go net ionic.

[CopperSmurf]

going net ionic:

2CuSO₄.5H₂O + HSO₃^- + OH^- + 2Cl^- ---> 2CuCl + 3SO₄^2- + 2H⁺ + 10H₂O

then you are suggesting that the copper ²⁺ is limiting.
So, what would the purpose of the NaOH when it is mixed with the bisulfite, if it does anything at all? Because now it seems odd that a strong base is making H⁺ as a product in the equation...

Thanks for the hint Borek.

*sorry for the edit, made typos near the end*

[CopperSmurf]

Cu²⁺ is limiting right?
I rebalanced the net ionic redox again, but since I had NaOH in the beginning, I had to get rid of the H⁺ on the product side.
So then...
2CuSO₄.5H₂O + HSO^3- + 3OH^- + 2Cl^- ---> 2CuCl + 3SO₄^2- + 12H₂O

and if I went by this equation, then NaOH would be limiting the Cu⁺ production, which then makes Cu⁺ limiting right?

Or... if I used the net ionic equation I made on the message right before this one, then only copper is limiting and not the NaOH or NaCl. Which net ionic equation should I really be using?

[Borek]

Looks like it is NaOH that is limiting. Your first reaction was in fact slightly wrong, it should be:

2CuSO₄^.5H₂O + 2NaCl + NaHSO₃ + 3NaOH -> 2CuCl + 3Na₂SO₄ + 12H₂O

Funny what has happened, the difference between your first reaction and the correct one is

2NaCl - 2NaOH = 2HCl - 2H₂O

which obviously doesn't make sense. Something went wrong during balancing and final effect was correct only accidentally.

Net ionic also means you should start with Cu²⁺

2Cu²⁺ + 2Cl^- + HSO₃^- + 3OH^- -> 2CuCl + SO₄^2- + 2H₂O

but it gives the same conclusion.

[CopperSmurf]

Thanks for pointing that out Borek.