Question

DAU COROANA! O solutie de soda caustica, de concentratie 20%, care contine 30 g de apa, se amesteca cu o alta solutie de soda caustica de concentratie 15%, care contine 40 g de apa. Care va fi concemtratia solutiei finale?

Answer 1

c1=20%
m apă1=30g
c2=15
m apă2=40g
ms1=md1+m apă 1$c 1 = \frac{md1}{md1 + m \:apa1} \times 100 \\c1(md1 + m \: apa1) = md1 \times100$
c1×md1+c1×m apă 1=md1×100
c1×m apă1=md1×100-c1×md1
md1×(100-c1)=c1× m apă 1
$md1 = \frac{c1 \times m \: apa1}{100 - c1} \\ md1 = \frac{20 \times 30}{100 - 20} = \frac{600}{80} = 7.5g$
ms2=md2+m apă2
$c2 = \frac{md2}{md2 + m \: apa2} \times 100 \\ c2(md2 + m \: apa2) = md2 \times 100$
c2×md2+c2×m apă2=md2×100
c2×m apă2=md2×100-c2×md2
md2×(100-c2)=c2×m apă2
$md2 = \frac{c2 \times m \: apa2}{100 - c2} \\ md2 = \frac{15 \times 40}{100 -15 } = \frac{600}{85} = 7.05g$
m apă=m apă1+m apă2=30+40=70g
md=md1+md2=7,5+7,05=14,55g
$c = \frac{md}{md + m \: apa} \times 100$
$c = \frac{14.55}{14.55 + 70} \times 100 \\ c = \frac{14.55}{84.55} \times 100 = 17.20\%$