Ionic EquilibriumHard
Question
Consider a weak base ' B ' of ${pK}_{b} = 5.699$. ' x ' mL of 0.02 M HCl and ' y ' mL of 0.02 M weak base ' B ' are mixed to make 100 mL of a buffer of pH 9 at $25^{\circ}C$. The values of ' $x$ ' and ' $y$ ' respectively are:
[Given: $log2 = 0.3010,log3 = 0.4771,log5 = 0.699$ ]
Options
A.
|
|
|
|
11.1 |
88.9 |
B.
|
|
|
|
42.7 |
57.3 |
C.
|
|
|
|
14.3 |
85.7 |
D.
|
|
|
|
85.7 |
14.3 |
Solution
| HCl | $$+ B \rightarrow {BH}^{+} + {Cl}^{-}$$ | ||
|---|---|---|---|
| 0.02 M | 0.02 M | ||
| x ml | y ml | ||
| $$t_{f}$$ | 0 | $$0.02y - 0.02x$$ | 0.02 x |
$${pOH = {pK}_{b} + log\left\lbrack \frac{\text{~Salt~}}{\text{~Base~}} \right\rbrack }{5 = 5.699 + log\left\lbrack \frac{\text{~Salt~}}{\text{~Base~}} \right\rbrack }{\frac{x}{y - x} = \frac{1}{5} }{6x = y }{7x = 100 }{x = \frac{100}{7}ml }{\& y = \frac{600}{7}ml}$$
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