Answer
$pH \approx 2.876$
Work Step by Step
1. Find the molar mass of $HClO_3$:
H: 1 x 1 = 1
Cl: 1 x 35.5 = 35.5
O: 3 x 16 = 48
1 + 35.5 + 48 = 84.5g/mol
2. Calculate the nº of moles, and the concentration of the solution.
nº of moles = mass $\div$ molar mass
nº of moles = 0.225 $\div$ 84.5
nº of moles $\approx$ 2.66 $\times$ $10^{-3}$
concentration = nº of moles $\div$ volume(L)
$C = \frac{2.66\times10^{-3}}{2}$
$C = 1.33 \times 10^{-3}M (HClO_3)$
3. Because $(HClO_3)$ is a strong base, and has 1 $H$:
$[HClO_3] = [H^+]$
$1.33 \times 10^{-3} = [H^+]$
4. Calculate the pH:
$pH = -log[H^+]$
$pH = -log(1.33\times10^{-3})$
$pH \approx 2.876$
