Question

You are making a pH 5.0 buffer with acetic acid (pKa = 4.75) and sodium acetate. You want the total concentration of acetate ([acetic acid] + [sodium acetate] ), to be 0.50 M. What concentrations of acetic acid and sodium acetate do you use to make your buffer? acetic acid sodium acetate

Answer 1

Let x be concentration of acetic acid Let be Concentration of sodium acetate y Now Given - pH = 5, pka = 4.75 Orx + y = 0.50M y = 0.50-2

Now using equation of pH

pH= pKa + log ([salt]/[acid])

Salt is sodium acetate = y

Acid is acetic acid = x

+ Now put all values given in ph equation pH = pka lug [CH₃COONa [CH3 Coon w 5 = 4.75 t log [y]. [x 1.77 0.50- M 18 x 1.778+x=0.50 a= 0.179 M Put Value of a 'in y = 0.50-2 y=0.50 -0.179 = 0. 32IM

Concentration of acetic acid = 0.179 M

Concentration of sodium acetate= 0.321M