[BioMajor]

I did a lab last week about chemical equilibrium, and I need to explain why the stock solution of .01M Fe(NO₃)₃ and KSCN (which is already a rust red color) turns a darker red when 5 drops of .1M Fe(NO₃)₃ is added to one well (1mL stock), and why it turns even a deeper red when 5 drops of 0.1M KSCN is added to another well of the same stock (1mL)? I'm thinking that it shifts everything to the right, but I can't exactly explain it? One well was the stock + 0.1M Fe(NO₃)₃ (darker red than stock), and the other well was stock + 0.1M KSCN.(even darker than when 0.1 Fe(NO₃)₃ was added to the other well). Why? I also need a net ionic equation to explain it... but as far as I know, it's the same reaction as the stock? Oh, everything is aqueous, btw.

Any help would be great!
Thanks!

[rabolisk]

There is a reaction between the two species, iron (III) nitrate and potassium thiocyanate. Addition of either one of these drives the reaction forward per Le Chatelier's principle. There are going to be spectator ions though. Based on solubility, what do you think they are?

[BioMajor]

NO₃^- and K⁺ are the spectators? I know it yields FeSCN²⁺, I'm just not exactly sure why it changes color further when it's the same reaction as the stock, just a higher molarity?

[rabolisk]

Yeah, I would say just that the reaction just produces more FeSCN²⁺. After all, the solution was already somewhat red to begin with.