Question

The pH of a buffer containing equal molar concentrations of a weak base and its chloride ($K_b$ for weak base $=2\times {10}^{-5},\log 2=0.3$) is:

• A. $5$
• B. $9$
• C. $4.7$
• D. $9.3$

Answer 1

The correct option is D $9.3$

Applying the equation
$pOH=\log \frac{\left[Salt\right]}{\left[Base\right]}-\log K_b$
$=\log 1-\log 2\times {10}^{-5}=4.7$
$pH=(14-4.7)=9.3$