Question

The dissociation constant of a weak monoacidic
base is 10-5. The pH of its 0.1 M solution will be
approximately equal to
( 1 ) 11
( 2 ) 8
( 3 ) 7.5
( 4 ) 10​

Answer 1

Answer:

pH = 11

Explanation:

[OH-] = √Kb ×C .... (ostwalds law)

= √1× 10‐⁵ × 0.1

= 10‐³ M

pOH = -Log 10‐³

= 3

pH = 14 - 3

pH = 11

Answer 2

The correct option about the pH of 0.1 M solution is ( 1 ) 11.

Given:

The dissociation constant of a weak monoacidic

the base is 10-5 and the concentration is 0.1M.

To Find:

The pH of 0.1 M solutions.

Solution:

To find the pH of 0.1M solutions we will follow the following steps:

As we know, the solution is a weak monoacidic base. so, the concentration of hydroxide ion is given by the formula:

$[ {OH}^{ - } ] = \sqrt{kc}$

Here, k is the dissociation constant of the weak monoacidic base, and c is the concentration of the solution.

Now,

$[ {OH}^{ - } ] = \sqrt{ {10}^{ - 5} \times 0.1 } = \sqrt{ {10}^{ - 6} } = {10}^{ - 3} mol {l}^{ - 1}$

Also,

POH = -log[OH]

Now, putting values of concentration of hydroxide ion we get,

$POH = - log( {10}^{ - 3} ) = - ( - 3)log10 = 3$

The sum of pH and pOH is equal to 14 at 298k temperature.

So,

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 3 = 11

Henceforth, The pH of 0.1 M solutions is 11.

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