2Na + 2H₂O = 2NaOH + H₂
Solutia finala nu va avea masa 100g si nici 2,3g, dar va fi 100g+2,3g-m(H₂) sau =100g+m(NaOH)-m(H₂O)consumat in urma reactiei...
la obtinerea unui mol de H₂ se consuma 2 de Na, deci noi avand 2,3g adica 0,1mol de Na, vom obtine 0,05mol H₂, si 0,1 mol de NaOH, m(H₂)=0,05mol*2g/mol=0,1g, m(NaOH)=0,1mol*40g/mol=4g
w(NaOH)=m(NaOH)*100%/m(sol)=4g*100%/(100+2,3-0,1)g=400/102,2=3,914%
