Question

1.Calculeaza masa solutilor:

a) Solutie de saramura( NaCl + H2O) de concentratie 25% ce contine 40g sare de bucatarie(NaCl).

b) Solutie apoasa de soda caustica( NaOH) de concentratie 20% ce contine 200g apa(H2O)

2. O solutie de acid clorhidric(HCl) are concentratiade 35% si densitatea 1,89% . Calculeaza masa de acid clorhidric ce se gaseste in 500 ml.

Answer 1

1. a) C=md/ms*100 => ms=md*100/C=40*100/25=160g sol. saramura

b) C=md/md+mH2O*100 => 20=md/md+200*100 => 20md+4000=100md => 80md=4000 => md=50g

ms=md+mH2O = 50+200 = 250g sol. NaOH

c) ro=ms/V=>ms=ro*V=1,89*500=945g sol. HCl

C=md/ms*100 => md=C*ms/100=35*945/100=330,75g HCl

Answer 2

1. a)
c=md×100/ms
ms=md×100/c 
ms=40×100/25 =40×4=160g solutie NaCl

1.b)
c/100 = md/(md+mH2O)
20/100 = md/(md+200)
1/5=md/(md+200)
5md=md+200
4md=200
md=200/4=50gNaOH
ms=md+mH2O
ms=50+200=250g solutie

2. ρ=ms/Vs
1,89=ms/500
ms=1,89×500 = 945g
c=md×100/ms
35=md×100/945
md=35×945/100
md=35×9,45=330,75g HCl