Răspuns:
ms1=200g
c1=25%
c2=45%
md?
c=mdx100/ms, unde ms= md+m,apa
md1= c1xms1/100= 25x200/100g=50g sare
c2= md2x100/ms unde md2=md1+md
ms2= ms1+md
45= (50+md)100/(200+md)
45(200+md)=100(50+md)
md=72,7g sare
T=27+273=>300K
V=5L
p=3atm
A,He=4g/mol
pV=niuRT UNDE niu=m/miu
pV= mRT/miu
3x5= mx0,082x300/4---> m=2,44g
Explicație: