Quick Question - EMF? (1 Viewer)

[Zokunu]

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2012exams/pdf_doc/2012-hsc-exam-chemistry.pdf

Question 14 please. StepbyStep? since i have no idea what to do here....

Thank you

 

[QZP]

Have you learnt how to use the standard potentials on the data sheet?

 

[Zokunu]

Have you learnt how to use the standard potentials on the data sheet?

Ye, what about them?

 

[strawberrye]

http://conqchem.cci.net.au/Exam12Frameset.htm-have a look at the explanation of answer for this question-it might clarify some things for you. Essentially, you need to recognise which species was being reduced and oxidised in this equation, and accordingly calculate the appropriate reduction/oxidation potential and get the voltage(EMF) of the cell by referring to the equations and potentials given on the HSC standard potentials table. Hope this helps a bit

 

[Zokunu]

http://conqchem.cci.net.au/Exam12Frameset.htm-have a look at the explanation of answer for this question-it might clarify some things for you. Essentially, you need to recognise which species was being reduced and oxidised in this equation, and accordingly calculate the appropriate reduction/oxidation potential and get the voltage(EMF) of the cell by referring to the equations and potentials given on the HSC standard potentials table. Hope this helps a bit

Thx strawberrye, i get how you get 0.77, but how did you get 1.36 as an EMF?

 

[strawberrye]

Thx strawberrye, i get how you get 0.77, but how did you get 1.36 as an EMF?

Essentially, the Fe2+ was oxidised to Fe3+, so from question 13-if you answered it correctly, you would have known that Cr2O2-7 is being reduced, so if you refer to its reduction equation and potential on the electric potential table you will see it as a positive voltage of 1.36V-that's how you get the 1.36 V. However, the explanation is not stating that 1.36 is the EMF, the overall EMF is 1.36-0.77 where you will get 0.59V as the overall EMF of the cell, and hence A is the answer.

 

[Zokunu]

Essentially, the Fe2+ was oxidised to Fe3+, so from question 13-if you answered it correctly, you would have known that Cr2O2-7 is being reduced, so if you refer to its reduction equation and potential on the electric potential table you will see it as a positive voltage of 1.36V-that's how you get the 1.36 V. However, the explanation is not stating that 1.36 is the EMF, the overall EMF is 1.36-0.77 where you will get 0.59V as the overall EMF of the cell, and hence A is the answer.

wow, i was looking at my EPT table on conquering chemistry, at there was no reduced one where it equals 1.36.

thx man