Question

Se amesteca 100g solutie de acid clorhidric de concentratie 20%cu 200g solutie de acid de concentratie 15%si cu 400g solutie de acid de concentratie 5%.concentratia procentuala finala a solutiei de acid clorhidric obtinute este a)17% b)7% c)10% d)18%

Answer 1

solutia 1 : ms1 = 100g    c1 = 20% ⇒ md1 = 20g
solutia 2 : ms2 = 200g    c2 = 15% ⇒ md2 = 30g
solutia 3 : ms3 = 400g    c3 = 5% ⇒ md3 = 20g
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ms final = ms1 + ms2 + ms3 = 700g
md final = md1 + md2 + md3 = 70g 
c = 70·100/700 = 10%