## Test #2 question 4

lauren chung 2f
Posts: 50
Joined: Fri Sep 29, 2017 7:03 am

### Test #2 question 4

On Test 2, it asks to calculate the standard potential for the galvanic cell,
U (s)| U+3 (aq) || V+2 (aq) | V (s)

Since
U+3 + 3e- --> U E= -1.79
V+2 + 2e- --> V E = -1.18
but U is the anode, so I made the equation
U --> U+3 + 3e- E= +1.79

Then I wrote
Ecell = Ecathode - Eanode
= -1.18 - (1.79)
= -2.97 V

Can someone tell me where I went wrong?

Xin He 2L
Posts: 38
Joined: Fri Sep 29, 2017 7:05 am

### Re: Test #2 question 4

You don't flip the signs of the cell potential when you flip the equation.

lauren chung 2f
Posts: 50
Joined: Fri Sep 29, 2017 7:03 am

### Re: Test #2 question 4

Can you explain why you don't flip the signs of the cell potential?

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

### Re: Test #2 question 4

For the equation Ecell = Ecathode - Eanode, it assumes you have not already flipped the sign of the anode. Therefore Ecell = -1.18-(-1.79).
However, you made the equation E=+1.79. In this case you have already flipped the sign and hence the eq is -1.18+1.79.

Cristina Sarmiento 1E
Posts: 52
Joined: Wed Nov 16, 2016 3:02 am

### Re: Test #2 question 4

When you flip the sign because you flip the equation, you must do Ecell = Ecathode + Eanode.
It is also helpful to know that for galvanic cells, the Ecell must always be positive.

Return to “Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams”

### Who is online

Users browsing this forum: No registered users and 2 guests