Se calculeaza cantit. de soda caustica pura
puritatea=p=mp.100:mt
mp=p.100:mt
mp=75.120:100=90g NaOH pura
Trebuie calculata cantit. de Na aflata in 90 g NaOH PUR
M NaOH=23+16+1=40------->1 mol=40g
40g NaOH------------23g Na
90 g-----------------------xg
x=90.23:40=51,75 g Na