Question

If a buffer solution is 0.250 M 0.250 M in a weak base ( K b = 8.0 × 10 − 5 ) Kb=8.0×10−5) and 0.540 M 0.540 M in its conjugate acid, what is the pH ?

Answer 1

Answer:

9.57

Explanation:

Given that:

$pK_{b}=-\log\ K_{b}=-\log(8.0\times 10^{-5})=4.1$

Considering the Henderson- Hasselbalch equation for the calculation of the pOH of the basic buffer solution as:

$pOH=pK_b+log\frac{[conjugate\ acid]}{[base]}$

So,  

$pOH=4.1+\log\frac{0.540}{0.250}=4.43$

pH + pOH = 14  

So, pH = 14 - 4.43 = 9.57