Ionic EquilibriumHard
Question
An acid-base indicator which is a weak acid has a pKIn value = 5.45. At what cocentration ratio of sodium acetate to acetic acid would the indicator show a colour half-way between those of its acid and conjugate base forms? [pKa of acetic acid = 4.75, log 2 = 0.3]
Options
A.4 : 1
B.6 : 1
C.5 : 1
D.3 : 1
Solution
pKa = 5.45
pH = pKHIn + log
⇒ pH = pKHIn = 5.45
For a Buffer solution
pH = pKa + log
⇒ 
pH = pKHIn + log
⇒ pH = pKHIn = 5.45For a Buffer solution
pH = pKa + log
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