impuritatile nu reactioneaza cu H2O
p=50%
p/100=mpura/mimpura => mpura=p*mimpura/100=50*230/100=115g Na pur
MNaOH=23+1+16=40g/mol
2*23g..............2*40g....1mol
2Na + H2O -> 2NaOH + H2
115g..............x=?.......y=?
x=115*80/46=200g NaOH
y=115/46=2,5moli H2
1mol H2...........22,4l
2,5moli..............z l
z=2,5*22,4=56l H2