Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Ferrous.Wheel on April 29, 2010, 01:21:24 AM
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When a chemical system is in equilibrium, reactant molecules still produce product molecules and product molecules produce reactant molecules. How do you test this statement using 14CNS- in which the carbon is radioactive carbon 14?
Fe^3+ (aq) + CNS^- <-------> Fe(CNS)^2+ (aq)
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Hey, sorry about that. Better read them-there rules then, 'ey?
Here are my ideas, as this is just an explanatory type answer, with no calcs, I'll just write my idea, it seems logical to me, but I am thinking I may be missing a big, obvious, glaring flaw in it...
Idea:
a possible answer may be to add ONE molecule of the radioisotope of the SCN- and then do repeated analysis of the two sides of the equation, (ie. test the aqueous solution or the CNS- precipitate) to see which side contains the radioactive bit, and observe that while the concentration of the two species is remaining the same, the radiocarbon atom is moving between both sides while in equilibrium.
Is there a flaw with this idea?
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Is there a flaw with this idea?
You can't add a single molecule and I doubt there is a precipitate present. To some extent you are on the right track. Remember reaction you are going to investigate is not the complexation reaction that you wrote, but rather
Fe(SCN)2+ + S14CN-<=> Fe(SCN)(S14CN)+ + SCN-
or at least that's how I read your original question.
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I am still at a mental standstill... I just don't know where to go from here. It's very frustrating, can you give me another nudge in the right direction, I feel like if I can just get the first step I can run with it... but that darn step is baffling me.