[EvilLock]

Currently working on a lab report for an introduction to qualitative analysis. I am really confused, and it isn't helping that we are doing this with a super short video because of the covid shutdowns.

It seems, from the gist of the crappy directions, that we are given a solution with 10 cations. The experiment is using 10 reagents to separate the cations into either (s) or (g) to be taken out of solution.

Here is where I'm confused. The reagent added is NaOH, observation is it turns litmus blue. The lab report wants the equation. My thinking on this is that by adding NaOH to the solution you get NH₄+(aq)+OH-(aq)=NH₃(g)+H₂O(l)

This turns litmus blue.

Next HCl is added and a white PPT forms.
Equation would be Ag+(aq)+Cl-(aq)=AgCl(s) the white PPT.

Then NH₄-, and NH₃ are added and a dark PPT is formed this would be Fe³⁺(aq)+3NH₃(aq)=Fe(OH)₃(s)+3NH₄-(aq)

So on and so forth. My question is am I even on a 10th of the correct path with this?

I'll try to add a pic of the table they included to see if maybe that helps too.

I don't want answers to this, more like confirmation that I'm on the correct path with my thinking.

[EvilLock]

I cant figure out how to insert my picture, but at the top it lists 10 cations, then it shows the addition of HCl and then it branches into a PPT of AgCl(s) on one side then the supernatant with all the cations except Ag+ , then the addtion of NH3, and NH4Cl, with the precipitate of Fe(OH)3(s) etc...

Let me know if I can somehow clarify this a little bit more, I think I understand the lab but it seems like I'm missing some glaring point, and just confusing myself more.

[Borek]

The reagent added is NaOH, observation is it turns litmus blue. The lab report wants the equation.

Litmus changes color with pH, no matter what cations/anions are present in the solution. It is just an acid/base equilibrium - you change protonated form into a non protonated one and they have different colors. Writing reaction equation is tricky, as litmus is a mixture of dyes. They share ta common chromophore though.

Next HCl is added and a white PPT forms.
Equation would be Ag+(aq)+Cl-(aq)=AgCl(s) the white PPT.

There are several cations that can get precipitated with Cl^-. Ag⁺ is the best known one.

Then NH₄-, and NH₃ are added and a dark PPT is formed this would be Fe³⁺(aq)+3NH₃(aq)=Fe(OH)₃(s)+3NH₄-(aq)

Something is off here. It Fe³⁺ were present it would precipitate much earlier, after NaOH addition. Actually NaOH addition would also already precipitate AgOH.

Your reaction equation is wrong - it is not balanced, there is no such thing as NH₄^-. You are right about Fe³⁺/Fe(OH)₃. Probably best approach is to treat ammonia solution as if it was just a base.

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