Chem Question

[HemlockGrey]

Ok, it's time for another stupid chem question from HemlockGrey. Can anyone let me know if sodium hydroxide plus oxalic acid (in equal amounts) yields h2c2o4oh? And what's the net ionic reaction for ammonium thiocyanate added to a solution of iron chloride? The teacher keeps assigning us these goddamn net ionic reaction quizzes without actually teaching us about them....("look it up" thanks asshole, where in the book? "Oh it's not in the book" thanks again asshole, then why am I hauling this 900 page piece of shit around all day...)

[tharkûn]

Can anyone let me know if sodium hydroxide plus oxalic acid (in equal amounts) yields h2c2o4oh?

What level chem are you in? The simple answer should be sodium bioxalate (I'm not sure if that is the covention your teacher wants - whatever is: Na+ HOOCCOO-) and one equivalent of water. The longer answer requires you to take into account everything up to activities and should be a mixture pretty damn close to the simple answer under most conditions.

Your answer is patently wrong. Acids don't take up hydoxyls unless you have something really screwball going on.

And what's the net ionic reaction for ammonium thiocyanate added to a solution of iron chloride?

Inasnwerable as posted. There are multiple iron chlorides due to different oxidation states. Beyond that I see nothing difficult about this ammonium thocyanate and whichever iron chloride you are using should be a straight forward ionic reaction.

[Kuroneko]

Can anyone let me know if sodium hydroxide plus oxalic acid (in equal amounts) yields h2c2o4oh?

That's not even balanced. Keep in mind the general rule that basic (hydroxide) and acidic reactants will produce water. Hence, NaOH + H₂C₂O₄ → NaHC₂O₄ + H₂O would be the best guess, particularly since it is in the specified proportion (as opposed to sodium oxalate).

And what's the net ionic reaction for ammonium thiocyanate added to a solution of iron chloride?

Unless there is something deeper going on (perhaps tharkûn can correct me on this), I don't think the nature of iron chloride matters much to the question as stated. Ammonium thicyanate should disassociate into NH₄⁺ and SCN⁻, ferric chloride into Fe³⁺ and 3Cl⁻ but ferrous chloride into Fe²⁺ and 2Cl⁻. The only chemically interesting thing for them to do seems to be to trade ions (necessarily, with some chlorine left over). This makes figuring out the complete reaction in either case not difficult, from which you can see which are the spectator ions, which cancel. Except for the charge of the final product (2+ vs. 1+) in the net ionic reaction, there is ultimately no difference.

[tharkûn]

Unless there is something deeper going on (perhaps tharkûn can correct me on this), I don't think the nature of iron chloride matters much to the question as stated. Ammonium thicyanate should disassociate into NH₄⁺ and SCN⁻, ferric chloride into Fe³⁺ and 3Cl⁻ but ferrous chloride into Fe²⁺ and 2Cl⁻. The only chemically interesting thing for them to do seems to be to trade ions (necessarily, with some chlorine left over). This makes figuring out the complete reaction in either case not difficult, from which you can see which are the spectator ions, which cancel. Except for the charge of the final product (2+ vs. 1+) in the net ionic reaction, there is ultimately no difference.

The big issue is knowing if it is ferric or ferrous, after that you will want to know which reactant is limiting.

The only major screwball stuff I can see is you might evolve enough heat to decompose some of the thiocyanate and ammonium if you do a real hash of it (more realisticly you'd have some transition metal contamination for catalysis); should this happen it will be readily apparent when people start dropping like flies.

[Kuroneko]

The big issue is knowing if it is ferric or ferrous, after that you will want to know which reactant is limiting.

That's the thing--it doesn't seem to make much difference to the original question. By the above reasoning, the ferric case is NH₄SCN + FeCl₃ → FeSCN²⁺ + NH₄Cl + 2Cl⁻, while the ferrous is NH₄SCN + FeCl₂ → FeSCN¹⁺ + NH₄Cl + Cl⁻. Both reactants seem equally limiting here; the only difference is the exact charges of the ions involved and how much chlorine is produced. This would mean that the net ionic equation is of the form Feⁿ⁺ + SCN⁻ → FeSCN⁽ⁿ⁻¹⁾⁺, where n is either 3 or 2 depending on the whether ferric or ferrous iron is used, respectively. Is there any deeper difference between ferric and ferrous chloride that would be relevant to the outcome?

[tharkûn]

Is there any deeper difference between ferric and ferrous chloride that would be relevant to the outcome?

Yes the ferrous iron is only in a +2 oxidation state which changes its ability to work as a transition metal catalyst. This becomes important as the heat evolved can drive ammonium chloride to ammonia (g) and hydrogen chloric acid (g/aq depending). You might also be able to drive to ferric sulfide if you start ferrous, but I can't recall that redox potential offhand.

Both reactants seem equally limiting here; the only difference is the exact charges of the ions involved and how much chlorine is produced.

Limiting, in this sense, refers to the quantity present. If you have four times as many mols of ammonium thiocyanate present then the limiting reactant will be iron chloride, if you have equal amounts then the ammonium thiocyanate will be limiting. This changes both concentration terms and the reactivity of the iron as a catalyst.

Long story short I know that you can react ferric chloride to ferric thiocyanate, ammonia, and hydrochloric acid (having actually done so). I'm not sure under what conditions ferrous chloride can do the same and unfortunately I can't find the mechanism for decomposing ammmonium chloride easily.

[HemlockGrey]

Thanks for the help...it was ferric chloride, I should probably have mentioned that. Also, when I wrote down the first thing, I was looking at another problem, typed in the wrong thing...it's a mess. Thanks for the help, though, the whole class has been been stuck in "review mode" for these equations for the last two months and its starting to wear on me.