Question

Determinati concentratia molara a urmatoarelor solutii:
a) in 200 mL solutie sunt dizolvati 20 mmoli NaOH
b) in 100 mL solutie sunt dizolvate 8g NaOH
c) se amesteca 200g solutie de NaOH 20% ( densitatea este 1,225 g/cm³) cu 36,74 mL apa.

Answer 1

a)200ml=0.2l , 20 mmoli=0.02moli=>CM=nr moli/volum=0.02\0.2=0.1 M; b)8 g NaOH,M=40 g/mol=>nr moli =8/40=0.2 moli NaOH,0.1 l solutie=>CM=0.2/0.1=2 M; c)200g solutie 20%=>20/100*200=40 g NaOH=>1 mol NaOH,Vsol=m/densitate=200/1.225=163.26 cm3=>Vsol finala=163.26+36.74=200cm3=0.2 l solutie NaOH=>CM=1/0.2=5 M.