Change in ion's electrical potential energy

[csimon1]

Homework Statement

A Na+ ion moves from inside a cell, where the electric potential is -70 mV, to outside the cell, where the potential is 0 V.

Uelec = ? eV

Homework Equations

I thought you would convert -70 mV to V (therefore it would be -.07) and multiply it by 1.6*10e-19 C. But it is rejecting my answer so I don't know what formula to use.

The Attempt at a Solution

See above.

 

[xcvxcvvc]

Homework Statement

A Na+ ion moves from inside a cell, where the electric potential is -70 mV, to outside the cell, where the potential is 0 V.

Uelec = ? eV

Homework Equations

I thought you would convert -70 mV to V (therefore it would be -.07) and multiply it by 1.6*10e-19 C. But it is rejecting my answer so I don't know what formula to use.

The Attempt at a Solution

See above.

First off, the change in voltage is positive. To see this, use final minus initial:
0 - (-.07) = +.07. Second, if you multiply by just 1.6e-19, your answer is in Joules. From what you've said, it seems to want eV. 1 eV is the amount of Joules required to move one electron through one volt. [U = qV = (1.6e-19 C) (1V) = 1.6e-19 J]

 

[csimon1]

Ohhh. Thank you.