masa de substanta care se pune se adauga si in masa de substanta dizolvata si in masa de solutie---> solutia initiala se va concentra
c= mdx100/ms
13/100= md1/180-----> md1=23,4g
md2= md1+70= 93,4g
ms2= ms1+70= 180+70g=250g
c2= 93,4x100/250=...................calculeaza si verifica daca c2>13%!!!