Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: avnis on April 03, 2011, 10:38:28 PM
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The solutions at the two Pb electrodes of a concentration cell were prepared as follows:
Cell A: A mixture of 1.00 mL of 0.0500 M Pb(NO3)2 with 4.00 mL of 0.0500 M KX (the soluble potassium salt of an unspecified monovalent ion X-).
Some PbX2(s) precipitates.
Cell B: 5.00 mL of 0.0500 M Pb(NO3)2.
The cell potential was measured to be 0.06800 V at 25 °C.
By use of the Nernst equation, determine the concentration (M) of Pb2+ in the solution of Cell A.
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You have to show your attempts at solving the question to receive help. This is a forum policy.
This is just a concentration cell, direct use of Nernst equation.
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You have to show your attempts at solving the question to receive help. This is a forum policy.
This is just a concentration cell, direct use of Nernst equation.
i am sorry i wasn't aware but, here is what i was thinking of doing i thought i would just pluging in the numbers but then i don't know the Ecell i mean the stand value, so i get stuck there.
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Can you start by writing down and balancing the chemical reaction(s) that take place?
What are the equations you need?
If you write all this down systematically, you will see which values you lack.
As for Ecell0, write down the equations taking place and you will see what it is.
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Can you start by writing down and balancing the chemical reaction(s) that take place?
What are the equations you need?
If you write all this down systematically, you will see which values you lack.
As for Ecell0, write down the equations taking place and you will see what it is.
ohk so i thought it would be pb and k that will cause the reaction right, but a friend of mine says it is pb and x so i if it pb and k i can solve it( it is a piece of cake), but if it x i am doomed :(, i am unable to decide which one it is
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what equilibrium is there in the one half cell, and which in the other?
and no, neither X nor K is used in the reaction
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what equilibrium is there in the one half cell, and which in the other?
and no, neither X nor K is used in the reaction
oh i haven't haven't thought of it like this
well in cell A it is a smaller concentration of pb ion and in cell B a larger so this cell will be driven by concentration difference so the electrons will flow from higher concentration to lower concentration
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what equilibrium is there in the one half cell, and which in the other?
and no, neither X nor K is used in the reaction
oh i haven't haven't thought of it like this
well in cell A it is a smaller concentration of pb ion and in cell B a larger so this cell will be driven by concentration difference so the electrons will flow from higher concentration to lower concentration
oh now i am officially lost !!!!!!
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what equilibrium is there in the one half cell, and which in the other?
and no, neither X nor K is used in the reaction
would it be lead ion and nitrate ions doing it
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well in cell A it is a smaller concentration of pb ion and in cell B a larger so this cell will be driven by concentration difference so the electrons will flow from higher concentration to lower concentration
indeed, so the only species participating in the reaction is lead.
Pb --> Pb2+ + 2 e- in one half
Pb2+ + 2 e- --> Pb in the other
what does this mean for Ecell0? (standard cell potential, where concentration is not factored in)
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well in cell A it is a smaller concentration of pb ion and in cell B a larger so this cell will be driven by concentration difference so the electrons will flow from higher concentration to lower concentration
indeed, so the only species participating in the reaction is lead.
Pb --> Pb2+ + 2 e- in one half
Pb2+ + 2 e- --> Pb in the other
what does this mean for Ecell0? (standard cell potential, where concentration is not factored in)
it means that it is zero.
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well in cell A it is a smaller concentration of pb ion and in cell B a larger so this cell will be driven by concentration difference so the electrons will flow from higher concentration to lower concentration
indeed, so the only species participating in the reaction is lead.
Pb --> Pb2+ + 2 e- in one half
Pb2+ + 2 e- --> Pb in the other
what does this mean for Ecell0? (standard cell potential, where concentration is not factored in)
it just meansEcell0 is zero so , now for he equation my Q will
Pb cell B/ Pb cellA
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it just meansEcell0 is zero
indeed. So try to solve it now.
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it just meansEcell0 is zero
indeed. So try to solve it now.
OHK got that now next part is saying
In Cell A, how many moles of X- have reacted with Pb2+?
i was doing thi converting the concentration of Pb into moles and that will be how any avaialbe to react and only that many will react but that isn't correct
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I assume they mean how many PbX2 has crystallized?
If your answer at 1) is correct, you have a concentration of Pb2+.
You then calculate how many moles of Pb2+ this is.
Your original number of moles of lead you can calculate from the lead nitrate solution you started with.
The difference is the number of moles that reacted
ps. use the numbers and formulas here if you want, then we can have a better look at where you might be going wrong