Na reactioneaza cu apa
2mol 2mol 2mol sau, in grame
2Na + 2H2O------> 2NaOH + H2
2x23g........2x18g,,,,,.......2x40g
23g............x= 18g..............y= 40g
rezulta o solutie formata din NaOH si restul de apa
c= mdx100/ms
md= m,NaOH= 40g
ms= md+m,apa m,apa= 178g-18g(masa consumata in reactie)= 160g
ms=40+160=> 200g
c= 40x100/200 %=........................calculeaza !!!!!