Răspuns:
A,Na=23g/mol
-calculez moli Na
niu=m/A=2,3/23mol=0,1mol
-deduc moli H2O si NaOH din ecuatia
2mol.........2mol.........2mol
2Na + 2H2O---> 2NaOH + H2
0,1mol...........x...............y
x= 0,1molH2O
y= 0,1molNaOH
-calculez masa de apa formata si masa de apa ramasa nereactionata
miu,H20=18g/mol
m,apa reactie= niuxmiu= 0,1x18g=1.8g
m,apa ramasa= 72-1,8=> 70,2g
-calculez masa de NaOH, stiind miu,NaOH= 40g/mol
m,niuxmiu=0,1x40g=4,gNaOH
calculez c% a solutiei alcatuita din 4gNaOH si70,2g H2O
C=mdx100/ms unde
md=4g
ms=md+m,apa= 4+70,2=>74,2g
c=4x100/74,2=5,4%
Explicație:
