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Submitted by Isidoraa on Thu, 01/09/2014 - 18:57
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Izracunaj maseni udio rastvora ako se u 600g 20% rastvora secera doda:
a) 200 g vode,
b) 80 g secera
c) 200 g vode i 80 g secera
Rjesenje: a) 0,15
b) 0,294
c) 0,227

milicaradenkovic's picture

milicaradenkovic - Thu, 01/09/2014 - 19:09

a) ms=w*mr=600*0.2=120 g

mru=mr+m(vode)=600+200=800 g

w=ms/mru=120/800=0.15

b) msu=ms+m(secera)=120+80=200 g

mru=mr+m(secera)=600+80=680 g

w=msu/mru=200/680=0.294

c) msu=ms+m(secera)=120+80=200 g

mru=mr+m(secera)+m(vode)=200+600+80=880 g

w=msu/mru=200/880=0.227

 

Isidoraa's picture

Isidoraa - Thu, 01/09/2014 - 20:26

Pod b) zar ne bi trebalo da je to 80g mr2 a ne ms2

milicaradenkovic's picture

milicaradenkovic - Thu, 01/09/2014 - 20:31

Pod b se masa secera ubacuje i u msu i mru.

Isidoraa's picture

Isidoraa - Sat, 01/25/2014 - 04:09

zasto bas tako

milicaradenkovic's picture

milicaradenkovic - Sat, 01/25/2014 - 08:40

Zato sto ti se menja i masa rastvora i masa rastvorene supstance.