Question

Coroana!Ajutor!!!In 400g solutie de hidroxid de sodiu de concentratie necunoscuta se adauga 15 g de hidroxid de sodiu.Solutia nou obtinuta are concentratia de 25%.Determina concentratia solutiei initiale!

Determina concentratia procentuala a solutiei obtinute prin amestecarea a doua solutii,una cu concentratia de 14%,iar cealalta cu concentratia de 25% si care se gasesc in raport masic 1 : 2.

Answer 1

problema 1.

ms1=400g

c1 ?

c1= md1x100/ms1---> md1= c1xms1/100= 4c1

md2= md1+15= 4c1+15

ms2= ms1+15= >415g

c2= 25= md2x100/ms2

25/100= (4c1+15)/415

100(4c1+15)=25x415----> c1=22,2%

problema 2

ms1/ms2=1/2

c3= (md1+md2)x100/(ms1+ms2)

   -=(14ns1+25ms2)/ (ms1+ms2)        impart si sus si jos cu ms2

     = (14x1/2+25)/(1/2+1)

     =32/1,5=21,33%