Equilibrium Question 814
Question: The degree of dissociation of 0.1 M 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 $ H_3{O^{+}} $ ion concentration in the resulting solution will be respectively
Options:
A) 0.02 and $ 3.125\times {10^{-4}} $
B) $ 1.25\times {10^{-3}} $ and 0.02
C) 0.02 and $ 1.25\times {10^{-3}} $
D) 0.02 and $ 8.0\times {10^{-12}} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ {\alpha_1}=0.005=\sqrt{K_{a}\times C_1} $ Molarity of diluted solution; $ 2\times 1=32\times M, $
$ M=\frac{1}{16}(C_2) $
$ {\alpha_2}=\sqrt{\frac{K_{a}}{C_2}}=0.005\sqrt{16}=0.02 $
$ H_3\overset{+}{\mathop{O}},=C_2{\alpha_2}=\frac{0.02}{16}=1.25\times {10^{-3}}M $
