It is seen from the given balanced equation of the repacement reaction that every mole of (CH_2)_n requires total 2nmol F_2.Here n mol goes to replace hydrogen and n mol goes to form 2n mol HF and thus one mole of (CF_2)_n is formed.
Molar masses of
F_2->38g"/"mol
(CF_2)_n->50ng"/"mol
Fluorine required for the production of 50ng (CF_2)_n is 2n mol or 76ng
So to prodoce 1kg (CF_2)_n we rrequire (76n)/(50n)kg=1.52kg Fluorine, if not recovered from HF produced as byproduct.
As 50% F_2 goes to form the byproduct HF,then its recovery will diminsh the net consumption by 50% and the consumption of Flurine for productio of 1kg (CF_2)_n then will be 50%of1.52kg=0.76kg
