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18/10/2021 11:37 am
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Calculate the pH of a solution containing 0.1 M HCO3- and 0.2 M CO32-
[K1 (H2CO3) = 4.2 × 10-7 × 10 and K2(HCO3-) = 4.8 × 10-11].
(a) 3.18
(b) 10.62
(c) 6.62
(d) 9.31
1 Answer
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18/10/2021 11:45 am
Correct answer: (b) 10.62
Explanation:
HCO3- → H+ + CO32-
K2 = \(\frac{[H^+][CO_3^{2-}]}{[HCO_3^-]}\)
= 4.8 × 10-11
[H+] = \(\frac{4.8 \times 10^{-11}[HCO_3^-]}{[CO_3^{2-}]}\)
= 4.8 × 10-11(\(\frac{0.1}{0.2}\))
pH = -log[H+]
= -log(4.8 × 10-11 x 0.5) = 10.62