Posted by me on Sunday, June 6, 2010 at 12:07am.
The electrochemical cell described by the cell notation has a standard emf (electromotive force) of 0.68 V. Calculate the value (kJ) for the standard free energy change of the cell. Round your answer to 3 significant figures.
Pt(s) l MnO2(s) l MnO4(aq), H+(aq) ll H+(aq), VO2+(aq), VO2+(aq) l Pt(s)

chemistry  me, Sunday, June 6, 2010 at 12:12am
i know how to do the problem but im not sure how the H+ effects the charge

chemistry  DrBob222, Sunday, June 6, 2010 at 12:39am
I think it's just delta G = nFE and H^+ doesn't fit in unless you are calculating K.

chemistry  me, Sunday, June 6, 2010 at 12:43am
but don't you need to incorporate the charge of H+ when finding n

chemistry  DrBob222, Sunday, June 6, 2010 at 12:57am
The charge must balance, yes, but the n is determined from MnO4 to MnO2 and VO2+ to VO2+ (why do you have two VO2+?one of them should be something else.

chemistry  me, Sunday, June 6, 2010 at 1:08am
oh, im sorry. i wrote it wrong. But i also had one more question. Do the coeffiecents have any effect on our calculation of "n"?

chemistry  me, Sunday, June 6, 2010 at 1:29am
for example this problem. the n is 6. how do we derive that?
The galvanic cell described by the balanced chemical equation has a standard emf of 0.10 V. Calculate the maximum electrical work (kJ) the cell has done if 1987.2 g of Cr2O72(aq) (Molar Mass  216.00 g/mol) reacts. Round your answer to 3 significant figures.
2Cr2O7^2(aq) + 16H^+(aq) → 3O2(g) + 4Cr^3+(aq) + 8H2O(l)

chemistry  DrBob222, Sunday, June 6, 2010 at 1:35pm
Yes, the coefficients matter. When calculating the n for a reaction, it is the TOTAL n for the TOTAL atoms.
Cr in Cr2O7^2 on the left is +5 for each Cr atom 6. That is 24 for 4 Cr atoms. On the right we have 4 Cr^+3 atoms at 12. Change is 126 = 6

chemistry  me, Sunday, June 6, 2010 at 6:47pm
Im sorry but i don't get it..... wouldnt the Cr in C2O72 have a 6+ charge? and Cr3+ has 3+ charge. So the left Cr would be 6*4 =24 and the right Cr is 3*4= 12 so wouldnt that be 2412= 12? what was your logic behind reducing it to 6? im sorry but this really confuses me
Answer This Question
Related Questions
 Chemistry  The voltaic cell described by the cell notation has a standard emf (...
 Chemistry  The electrochemical cell described by the balanced chemical equation...
 Chem  The galvanic cell described by the cell notation has a standard emf (...
 chemistry  The electrochemical cell described by the balanced chemical equation...
 chemistry  The electrochemical cell described by the cell notation has a ...
 chemistry(check my steps)  The electrochemical cell described by the cell ...
 chemistry  The electrochemical cell described by the balanced chemical reaction...
 Chem  The electrochemical cell described by the balanced chemical equation has ...
 chemistry  The electrochemical cell described by the cell notation has an Eo of...
 chemistry  The electrochemical cell described by the cell notation has an Eo of...
More Related Questions