Question

Calculate the p"' of 0.90M HPO,?Ka HPOA≥ = 4.5 x 10-13(a) 7(b) 14(c) 12.3(d) 8.20(e) 6.20

Answer 1

Answer

(e) 6.20

Explanation

The pH of the solution can be calculated using the formula below:

$pH=\frac{1}{2}pKa-\frac{1}{2}log\text{ }c$

Note that:

$pKa=-log\text{ }Ka$

Put Ka = 4.5 x 10⁻¹³ into the pKa formula:

$pKa=-log(4.5\times10^{-13})=12.35$

Put pKa = 12.35 and c = 0.90 into the pH formula above:

$\begin{gathered} pH=\frac{1}{2}(12.35)-\frac{1}{2}(log\text{ }0.90) \\ \\ pH=6.175-\frac{1}{2}(-0.0458) \\ \\ pH=6.175+0.0229 \\ \\ pH=6.1979 \\ \\ pH\approx6.20 \end{gathered}$

The pH = 6.20

The correct option is (e) 6.20