A solution is prepared by dissolving 0.23 mol of hypochlorous acid and 0.27 mol
ID: 1050720 • Letter: A
Question
A solution is prepared by dissolving 0.23 mol of hypochlorous acid and 0.27 mol of sodium hypochlorite in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the ________ present in the buffer solution. The Ka of hypochlorous acid is 1.36 10-3. Select one:
a. hypochlorous acid
b. H2O
c. H3O+
d. hypochlorite ion
e. This is a buffer solution: the pH does not change upon addition of acid or base.
Explanation / Answer
The solution contains hypochlorous acid and sodium ion and hypochlorite ion in solution and acts as buffer.
On adding acid, the H+ ions from acid reacts with hypochlorite ion and forms hypochlorous acid and this is almost unionized due to common ion effect of hypochlorite ion and thus pH of solution do not increase drastically
ClO-(aq) + H+(aq) ------> HClO(aq)
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