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18/10/2021 11:57 am
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The degree of dissociation of 0.1M weak acid HA is 0.5%. If 2 mL of 1.0 M HA solution is diluted to 32 mL the degree of dissociation of acid and H3O+ ion concentration in the resulting solution will be respectively
(a) 0.02 and 3.125 × 10-4
(b) 1.25 × 10-3 and 0.02
(c) 0.02 and 1.25 × 10-3
(d) 0.02 and 8.0 × 10-12
1 Answer
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18/10/2021 12:16 pm
Correct answer: (c) 0.02 and 1.25 × 10-3
Explanation:
α1 = 0.005 = \(\sqrt{K_a \times C_1}\)
Molarity of diluted solution; 2 x 1 = 32 x M
M = \(\frac{1}{16}(C_2)\)
α2 = \(\sqrt{\frac{K_a}{C_2}}\) = 0.005√16 = 0.02
H3O+ = C2α2 = \(\frac{0.02}{16}\)
= 1.25 × 10-3