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Acidic Buffer Action

A 30 mL solut...

Question

A $30 m L$ solution of $0.2 M C H_{3} C O O H$ is titrated with $0.2 M N a O H$ . Find the $p H$ of the solution when $10 m L$ of $N a O H$ has been added.
Given $p K_{a} (C H_{3} C O O H) = 4.74$

5.04

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4.44

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3.54

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4.04

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Solution

The correct option is B 4.44
mmol of $C H_{3} C O O H = 30 \times 0.2 = 6$
mmol of $N a O H = 10 \times 0.2 = 2$

$C H_{3} C O O H (a q) + N a O H (a q) \to C H_{3} C O O N a (a q) + H_{2} O (l) I n i t i a l l y : 6200 F i n a l : 4022$

After titration we can see that $4 m m o l$ of $C H_{3} C O O H$ and $2 m m o l$ of $C H_{3} C O O N a$ are present.
$Final Concentration = \frac{Moles}{Total Volume}$
Total Volume $= 30 + 10 = 40 m L$
$[C H_{3} C O O H] = \frac{4}{40} M$
$[C H_{3} C O O N a] = \frac{2}{40} M$
An acidic buffer is formed. So,
$p H = p K_{a} + l o g (\frac{[C H_{3} C O O N a]}{[C H_{3} C O O H]}) p H = 4.74 + l o g ⎛ ⎝ \frac{\frac{2}{40}}{\frac{4}{40}} ⎞ ⎠ p H = 4.74 + l o g (\frac{1}{2}) = 4.74 - 0.3 p H = 4.44$

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Similar questions

Q. A

50 m L

solution of

0.2 M C H_{3} C O O H

is titrated with

0.2 M N a O H

. Find the

p H

of solution when:
(a)

0 m L N a O H

is added (

p H_{i n i t i a l}

)
(b)

10 m L

N a O H

has been added (

p H_{10 m L}

)

Given:

K_{a} (C H_{3} C O O H) = 1.8 \times 10^{- 5}

20 m L

0.2 M C H_{3} C O O N a

solution is titrated against

0.1 M H C l

. Calculate the

p H

of solution when

10 m L H C l

has been added.
Given:

p K_{a} (C H_{3} C O O H) = 4.74

Q. A

50 m L

solution of

0.2 M C H_{3} C O O H

is titrated with

0.2 M N a O H

. Find the

p H

of solution when:
(a)

0 m L N a O H

is added (

p H_{i n i t i a l}

)
(b)

10 m L

N a O H

has been added (

p H_{10 m L}

)

Given:

K_{a} (C H_{3} C O O H) = 1.8 \times 10^{- 5}

Q. A solution of weak acid

H A

was titrated with base

N a O H

. The equivalence point was reached when

36.12 m L

0.1 M

N a O H

has been added. Now

18.06 m L

0.1 M

H C l

were added to titrated solution, the

p H

was found to be

4.92

. What will be the

p H

of the solution obtained by mixing

10 m L

0.2 M

N a O H

and

10 m L

0.2 M

H A

Q. The

p H

of a solution obtained by mixing

100 m L

0.2 M

C H_{3} C O O H

with

100 m L

0.2 M N a O H

will be: (

p K_{a} f o r C H_{3} C O O H = 4.74

)

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Acidic Buffer Action

Standard XII Chemistry

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A 30 mL solution of 0.2 M CH3COOH is titrated with 0.2 M NaOH. Find the pH of the solution when 10 mL of NaOH has been added. Given pKa(CH3COOH)=4.74

A $30 m L$ solution of $0.2 M C H_{3} C O O H$ is titrated with $0.2 M N a O H$ . Find the $p H$ of the solution when $10 m L$ of $N a O H$ has been added.
Given $p K_{a} (C H_{3} C O O H) = 4.74$