Calcium metal is obtained by direct electrolysis of molten cacl2. if a metallurgical electrolysis apparatus operates at 28.70 a, how many grams of calcium metal will be produced in 12 hours?

There is 1 mole of electrons = 96500C and Ca = 40 
Ca2+  + 2e --->Ca
Base on the formula above it means that there are 2 moles of electrons to produce 1 mole of calcium.

96500C x 2 = 193000C

193000C electricity produce 40g Calcium

Coulombs = Amps x seconds   (28.70A for 12 hours)
= 28.70A x 12 x 60 x 60 C
= 1 239 840 C

This amount of electricity will produce 

=1239840 / 193000 x 40g Calcium
= 6.42 x 40 g Calcium
= 256.96 g

So there will be 256.96g of Calcium metal that will be produced in 12 hours. 

Yes it would be a physical change.