Răspuns :
m,Na=23g/mol
niu= m/M= 4,6/23g= 0,2molNa
2mol.......2mol..........2mol........1mol
2Na + 2H2O------> 2NaOH + H2
0,2mol..x= 0,2mol.....y=0,2mol....z=0,1mol H2
m,NaOH= niuxM= 0,2X40g= 8g....reprezinta md,in solutia data
m,apa intrata in reactie= 0,2molx18g/mol= 3,6g
c=mdx100/ms--> ms= 8x100/20g= 40g sol.
dar m,s= md+mapa=> m,apa= 40-8g= 32g
m,apa adugata= 32--m,apa intrata in reactie= 32-3,6g=.................calculeaza !!!