[chay722]

I have the reaction 2AgNO3 + Na2CrO4 --> Ag2CrO4 + 2Na(NO3). I need to calculate the concentration of Na + in the liquid phase of this mixture. There is 100 ml of .1 M AgNO3 and 100 ml of .1 M Na2CrO4 mixed together in a 500 ml beaker. How would I determine the concentration of the Na +? What do they mean about it being in the liquid phase? Would that be it on the reactant side of the product side of the reaction?

[Arkcon]

They probably shouldn't have said liquid phase, it might have been easier on you if the said aqueous phase.  In that they want you to ignore the Na in the solid precip, which you know from your other posts is the Ag₂CrO₄ -- which contains no Na+, so it's dumb of them twice.

They ask you to determine how much Na+.  To start with, how much is there?

[chay722]

so I am solving for the concentration of the 2NaNO3, correct?

[chay722]

I mean, I am solving for the concentration of the Na+ from the 2NaNO3, correct?

[Arkcon]

Yes, there you go, correct the second time.  But, what if the amounts aren't stoichiometric, if there is excess reactant?  But in that case, does the problem become more difficult, or simpler?

[chay722]

Thank you. I believe I have figured out the answer. Thank you very much for the help.

[Arkcon]

Funny question wasn't it, asking you for the concentration of a spectator ion.  Maybe, the answer to this problem, will be used as the definition of spectator ion, on your next exam.