Răspuns:
c=44/3=14.(6)% =aprox= 14.67%
Explicație:
Masa initiala de substanta este: ms=150g
Masa de sare dizolvata initial este md.
Concentratia initiala: c=md×100/ms
Sau c×ms=100×md
Acum se adauga 10g sare:
md2=md+10
ms2=ms+10=150+10=160g
Concentratia este: c2=md2×100/ms2=20%
Sau c2×ms2=100×md2
Deci avem:
c×ms=100×md
c2×ms2=100×md2=100(md+10)=c×ms+1000
Numeric:
20×160=150×c+1000
3200=150×c+1000
2200=150×c
Deci concentratia initiala a fost:
c=2200/150=220/15=44/3=14.(6)%