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Standard XII

Chemistry

Electrolytes

Calculate the...

Question

Calculate the pH of an acidic buffer solution containing $1.2 M C H_{3} C O O N a$ and $0.8 M C H_{3} C O O H$ .
For acetic acid $K_{a} = 1.8 \times 10^{- 5}$

4.92

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3.66

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6.89

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5.88

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Solution

The correct option is A 4.92
$p K_{a} = - l o g (K_{a}) p K_{a} = - l o g (1.8 \times 10^{- 5}) p K_{a} = (5 - 0.26) = 4.74$
$p H$ for acidic buffer:

$p H = p K_{a} + l o g \frac{[s a l t]}{[a c i d]}$
$p H = p K_{a} + l o g \frac{[C H_{3} C O O N a]}{[C H_{3} C O O H]}$
$p H = 4.74 + l o g (\frac{1.2}{0.8}) p H = 4.74 + l o g (1.5) p H = 4.74 + 0.18 = 4.92$

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Similar questions

Q. What will be the new

p H

0.01 m o l

N a O H

is added to a

1 L

buffer solution that is

0.1 M

in acetic acid

(C H_{3} C O O H)

and

0.1 M

in sodium acetate

(C H_{3} C O O N a)

?
Dissociation constant

K_{a}

of acetic acid at

25^{\circ} C

1.8 \times 10^{- 5}

Q. The pH of a buffer solution containing 2.0 mol per litre

C H_{3} C O O N a

and 1.5 mol per litre

C H_{3} C O O H

is: (

K_{a}

for acetic acid is

1.8 \times 10^{- 5})

Q. A buffer solution of

p H = 5.74

is to be prepared using

C H_{3} C O O H

and

C H_{3} C O O N a

. Find the concentration of sodium acetate to be added to

0.01 M

solution of

C H_{3} C O O H

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

Take

l o g (1.8) = 0.26

Q. Assertion: On mixing equal volumes of 1 M

H C l

and of 2 M

C H_{3} C O O N a

, an acidic buffer solution is formed.
Reason: The resultant mixture contains

C H_{3} C O O H

and

C H_{3} C O O N a

which are parts of acidic buffer.

Q. The pH of a buffer solution containing 2.0 mol per litre

C H_{3} C O O N a

and 1.5 mol per litre

C H_{3} C O O H

is: (

K_{a}

for acetic acid is

1.8 \times 10^{- 5})

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Electrolytes

Standard XII Chemistry

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Calculate the pH of an acidic buffer solution containing 1.2 M CH3COONa and 0.8 M CH3COOH. For acetic acid Ka=1.8×10−5

The correct option is A 4.92pKa=−log(Ka)pKa=−log(1.8×10−5)pKa=(5−0.26)=4.74 pH for acidic buffer: pH=pKa+log[salt][acid] pH=pKa+log[CH3COONa][CH3COOH] pH=4.74+log(1.20.8)pH=4.74+log(1.5)pH=4.74+0.18=4.92

Calculate the pH of an acidic buffer solution containing $1.2 M C H_{3} C O O N a$ and $0.8 M C H_{3} C O O H$ .
For acetic acid $K_{a} = 1.8 \times 10^{- 5}$