Question

If a buffer solution is 0.190 M in a weak acid ( a=3.6×10−5) and 0.480 M in its conjugate base, what is the pH?

Answer 1

Solution :

$pk_b = -log ( K_b)\\\\pk_b = - log ( 3.6 \times 10^{-5})\\\\pk_b = 4.44$

We know, pH of this solution :

$pH = pK_a + log ( \dfrac{|conjugate\ base|}{|weak \ acid|}\\\\pH = 4.44 + log(\dfrac{0.480}{0.190})\\\\pH = 4.44 + 0.40\\\\pH =4.84$

Hence, this is the required solution.