I have a 250.0 mL solution which contains .100 M hypochlorous acid and .100 M so

Question

I have a 250.0 mL solution which contains .100 M hypochlorous acid and .100 M sodium hypochlorite. 122 mL of hydrogen chloride gas bubbles through the solution at normal room pressure (1.00 atm) and temp (25 celsius). If all the hydrogen chloride reacts and the solution's volume remains the same during the reaction, what is the pH of the resulting solution. The pKa of hypochlorous acid is 7.53.

I'm pretty sure this question has added information. I don't think I need to care about the 250.0 mL or the hydrogen chloride gas bubbling?

Explanation / Answer

HOCl + NaOCl mixture can act as a buffer.

HOCl millimoles (acid) = 250 x 0.1 = 25

NaOCl millimoles (salt)= 250 x 0.1 = 25

additional added HCl volume = 122ml = 0.122 lit

PV = n RT

P = (n/V) RT

P = M RT

M = P/RT = 1 / 0.0821 x 298

M = 0.040

millimoles of additional added (C) = 0.040 x 122= 4.99 = 5 (rounding of)

For acidic buffer

Henderson-Hasselbalch equation

pH = pKa + log[salt/acid]

on addition of

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