Electolysis?

Question

Neglect overpotential and determine the minimum potential required to electrolyze molten CrCl3.
Possible answers: 0.8V, 1.1V, 1.4V, 1.7V, 2.0V, 2.3V

b)How grams of Cr would be deposited and
c)how many liters of Cl2 gas would be produced at 184 degree C and 1.09 atm by passing a current of 26.0 A for 16.0 hrs?

Answer 1

First question, thermodynamics. You need to know the free energy of formation of liquid CrCl3. you can probably get away with using the free energy of formation of the solid compound as an approximation. Then use

charge x voltage = free energy

3 (per CrCl3) x 96485 coulomb x E volts = -DeltaHf(CrCl3)

Second question, b and c:

Lots of people have problems with this. Really, it is just a balancing act, with coulombs (amps x sec) as one of your reagents.

amps x sec = Coulombs. 96,485 coulombs = 1 Faraday = 1 mole electrons. Each Cr requires 3 electrons.

Using this information, you can balance the reducing agent (electric charge) against the amount of material reduced. For (c), the principle is the same, except that this time the electrons are being removed. Remember to consider how many electrons are removed to make each Cl2.