Question

Calculati cantitatea de soda caustica (g,moli) ce trebuie adaugata peste 200cm³ solutie de soda caustica de concentratie 28%(densitatea=1,31g/cm³ pentru ca solutia sa devina de concentratie 50 % !! 

Answer 1

p=ms/V⇒ms=p*V
ms=1.31g/cm³*200cm³
ms=262g

c₁=md₁*100/ms
md₁=c₁*ms/100
md₁=28*262/100
md₁=73.36g

c₂=md₂*100/ms
md₂=c₂*ms/100
md₂=50*262/100
md₂=131g

masa de soda caustica necesara=131-73.36=57.64g NaOH

Masa molara NaOH=23+16+1=40g/mol
1mol..............................40g
x moli..........................57.64
x=57.64*1/40=1.441moli NaOH