Question

An amount of 35.67 mg HCl is added to distilled water and the total solution volume is made to one litre. The atomic weights of H and Cl are 1 and 35.5, respectively. Neglecting the dissociation of water, the pH of the solution, is

• A. 2.50
• B. 3.50
• C. 3.01
• D. 2.01

Answer 1

The correct option is C 3.01

$36.5gmofHCldissociatesto1gmof{H}^{+}$

$\Rightarrow 1gmofHCldissociatesto\left(\frac{1}{36.5}\right)gmof{H}^{+}$

$\Rightarrow 35.67mgi.e.,35.67\times {10}^{-3}gmofHCldissociatesto(\frac{1}{36.5}\times 35.67\times {10}^{-3})gmof{H}^{+}$

$=(\frac{1}{36.5}\times 35.67\times {10}^{-3})$mole of $H^{+}$

As 35.67 mg is added to distilled water to form a solution of 1 lit.

$\therefore$ Concentration of $H^{+}$

$\left[H^{+}\right]=[\frac{1}{36.5}\times 35.67\times {10}^{-3}]\frac{mol}{lit}$

$=0.9773\times {10}^{-3}mol/lit$

$\therefore pH=-lo{g}_{10}\left[H^{+}\right]$

$=-lo{g}_{10}[0.9773\times 1^{-3}]=3.01$