pojedinacne koncentracije 76

Tina Trezic's picture

Koliko iznosi pojedinacne koncentracije  CH3COOH i CH3COONa u rastvoru pufera cija je pH 5,60 ako zbir koncentracija CH3COOH i CH3COONa iznosi 0,2 mol/dm3. (Ka=1,8*10-5

milicaradenkovic's picture

CH3COOH--------------->CH3COO- + H+

pH=5.60 pa je {H+}=2.5*10(-6) mol/l

{CH3COOH}+{CH3COONa}=0.2 mol/l

Ka={CH3COO-}*{H+}/{CH3COOH}

1.8*10(-5)=(0.2-{CH3COOH})*2.5*10(-6)/{CH3COOH}

{CH3COONa}=0.2-{CH3COOH}

CH3COONa------------->CH3COO- + Na+

{CH3COO-}={CH3COONa}

1.8*10(-5)*{CH3COOH}=2*10(-7)-2.5*10(-6)*{CH3COOH}

2.05*10(-5)*{CH3COOH}=5*10(-7)

{CH3COOH}=5*10(-7)/2.05*10(-5)=0.0244 mol/l

{CH3COONa}=0.2-0.0244=0.1756 mol/l