3.
A.
ms = md+m.apa = 25+125 = 150g sol.
c% = mdx100/ms
= 25x100/150 = 16,67%
B.
ms = 300g, c% = 20%
c% = mdx100/ms
=> md = msxc%/100
= 300x20/100 = 60 g zahar
C.
ms1 = 300g, c1% = 10%
ms2 =?g , c2% = 25%
c% = mdx100/ms
=> md1 = ms1xc1/100
= 300x10/100 = 30g acid clorhidric dizolvat
notam m.apa.evap. = a
ms2 = ms1 - a
c2% = mdx100/ms2
=> 25 = 30x100/(300-a)
=> a = m.apa.evap. = 4500/25 = 180 g apa evaporata
facem proba de calcul
md = 30g
ms2 = 300-180 = 120g
c2% = 30x100/120 = 25%, deci verifica calculul de mai sus
D.
ms1 = 200g, c1% = 40%
ms2 = 300g , c2% = 20%
ms.final = ms1 + ms2 = 200+300 = 500g sol. finala
din fiecare sol calc. md
c% = mdx100/ms
=> md1 = ms1xc1%/100
= 200x40/100 = 80 g
=> md2 = ms2xc2%/100
= 300x20/100 = 60g
=> md.final = md1 + md2 = 80+60 = 140 g
=> c%.final = md.finalx100/ms.final
= 140x100/500 = 28%
