1) What is the pH of a hypochlorous acid/sodium hypochlorite buffer in which the
ID: 562670 • Letter: 1
Question
1) What is the pH of a hypochlorous acid/sodium hypochlorite buffer in which the concentration of the weak acid component is 0.115 M and the concentration of the conjugate base is 0.139 M? Ka = 2.90E-08
2) The pH of a hypobromous acid/sodium hypobromite buffer in which the concentration of the weak acid component is 0.280 M and the concentration of the conjugate base is 0.110 M is 8.19. Suppose 0.59 g of solid NaOH are added to 100 mL of this buffer solution. What is the pH after the addition? ka=2.50E-09
Explanation / Answer
1)
pKa = -log Ka = -log (2.90 x 10^-8) = 7.54
pH = pKa + log [base / acid]
pH = 7.54 + log (0.139 / 0.115)
pH = 7.62
2)
pKa = 8.60
molarity of NaOH = ( 0.59 / 40 ) / 0.1 = 0.148 M
pH = pKa + log [base + NaOH / acid - NaOH]
pH = 8.60 + log (0.110 + 0.148 / 0.280 - 0.148)
pH = 8.89
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