a).
m.apa = 180 g , md=? g
ms = md+m.apa
c= mdx100/ms => 18 = mdx100/(189+md)
=> 3402 + 18md = 100md
=> md = 41,49 g sare
facem proba:
c= 41,49x100/(189+41,49) = 18% , deci verifica calculul
b).
ms2 = ms1 - m.apa.evap (a)
=> a = ms2-ms1
ms2 = mdx100/c2 = 41,49x100/12 = 345,75
=> a = ms2-ms1 = 345,75-230,49 = 115,26 g apa
c).
c3 = 23% , md.final = ?g
md.final = 41,49 + b
ms.fin = 345,75 + b
=> 23 = (41,49+b)100/(345,75+b)
=> 4149 + 100b = 7952,25 + 23b
=> b = 49,40 g sar adaugata...
facem proba:
c = 90,89x100/395,15 = 23% , deci verifica
d).
regula dreptunghiului:
66% -------------------------> 6 p. sol. 66%
l l
l 16% l
l l
10% --------------------------> 50 p. sol 10%
--------------------------------------------
total = 56 p. sol. 16%
56 p. sol total ........ 6 p. sol 66% ......... 50 p. sol 10%
n ................................. m ........................... 500 g
m = 500x6/50 = 60 g sol. 66%
e).
ms.f = ms1 + a
c1 = 30% => md = ms1xc1/100 = 400x30/100
= 120 g
c2 = 24% => ms,f = mdx100/c2 = 120x100/24
= 500 g
m.apa adaugata = ms2-ms1 = 500-400 = 100 g apa
f).
ms1 = 80 g , c1 = 4%
=> md1 = 80x4/100 = 3,2 g
ms2 = 160 g , c2 = 40%
md2 = 160x40/100 = 64 g
a = X = ? , c3 = 33,538%
ms.f = ms1+ms2+a = 80x+160+a
md.f = md1+md2+a = 3,2x64+a
33,538 = (67,2+a)100/(240+a) =
=> 8049,12 + 33,538a = 6720 + 100a
=> a = X = 20 g
