How much electricity in terms of Paradays
is reduired to produce ?
( 20.0 g of ca from molten calle
(2)81g of AL from molten Al2o3
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Answer:
(i)
The balance reaction will
The charge on Ca in CaCl2
Ca + 2Cl = 0
Cl has –1 charge so that
Ca + 2(–1) = 0
Ca = 2
We have to get 2o g Ca from Ca2+
Number of required moles = mass / molar mass
Molar mass of Ca is 40 g/mol and required mass of Ca is 20 g
Hence number of moles = 20/40 = 0.5 mol
Electricity required to produce 1 mol of calcium = 2 F
The electricity required to produce 0.5 mol of calcium
= 0.5 × 2 F
= 1 F
(ii)
Charge on Al in Al2O3
2Al + 3O = 0
Oxygen has –2
2Al +3(–2) = 0
Al = 3
Change transfer n = 3
Charge required for 1 mol of Al = 3F
Number of moles of Al = 40 /27 = 1.48
The electricity required to produce 1.48 mol of Al = 1.48 × 3 F
= 4.44 F
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