Question

Calculati concentratia procentuala masica a unei solutii de NaOH, obtinuta prin reactia a 4,6 g de sodiu cu 300 g apa. Eu am calculat si mi-a dat la final concentratia=2,59%, dar m-am uitat peste barem si scrie ca e 2,63% concentratia.

Answer 1

n= m/M;  n= 4,6g/23g/mol= 0,2molNa
2mol   2mol      2mol
2Na+2H20--> 2NaOH+H2
0,2......0,2........0,2
md= 0,2molx40g/mol=8gNaOH
m,apa= 0,2molx18g/mol= 3,6g apa reactionata
m,apa ramasa= 300-3,6--> 296,4g H2O
ms=md+m,apa= 8+296,4= >304,4g
c= 8x100/304,4