Adry cell does 7.5 j of work through chemical energy transfer 5.00c between terminals of the cell . what is the electric potential between the two terminals?

Here's a useful factoid that you don't hear about very often:

1 volt means 1 Joule per Coulomb.

When 1 coulomb of charge falls or gets lifted through 1 volt potential difference, it gains or loses 1 Joule of energy.

If you want to lift 5 coulombs to a height of 1 volt, you have to give it 5 joules.

If you actually give those 5 coulombs 7.5 joules instead, they'll rise up to 1.5 volts above the potential where they started. The flowed through a potential DIFFERENCE of 1.5 volts.

(If they started at a point that's connected to the Earth, like a water pipe or a metal flagpole, then their new potential is 1.5 volts, because we define zero as the potential of the ground.)