Question

Se ard 20 g calciu.Peste oxidul rezultat se adauga 500g Apa!Concentratia substantei obtinute este:a.)70%;b.)7%c.)14 %

Answer 1

2 Ca + O2 =>2 CaO
m Ca = 20 g
2x 40 g/mol Ca.... 2 x 56 g/mol CaO
   20 g Ca ...............a  g CaO 
a = 20 x 2 x 56 / 2 x 40 = 28 g CaO

m H2O = 500 g
m solutie = m H2O + m CaO 
m solutie = 500 g + 28 g = 528 g sol CaO
c = md/ ms x 100
c= (28 g CaO / 528 g sol CaO) x 100 = 5.303%