Equilibrium Question 365
Question: 0.1 mole of CH3NH2 (Kb = 5 ´ 10-4) is mixed with 0.08 mole of HCl and diluted to one litre. What will be the H+ concentration in the solution’ [IIT 2005]
Options:
A) 8 ´ 10-2 M
B) 8 ´ 10-11 M
C) 1.6 ´ 10-11 M
D) 8 ´ 10-5 M
Show Answer
Answer:
Correct Answer: B
Solution:
CH3NH2 + HCl $ \xrightarrow{{}} $
$ CH_3NH_3^{+}C{l^{-}} $ 0.1 0.08 0 0.02 0 0.08 (Basic buffer solution)
pOH = pKb + log $ \frac{0.08}{0.02} $ = pKb + 0.602 = 3.30 + 0.602= 3.902 \ pH = 10.09 [H+] = 7.99 ´ 10-11 » 8 ´ 10-11 M
