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Byju's Answer

Standard XII

Chemistry

Lewis Theory

In the dissoc...

Question

In the dissociation of $N H_{4} O H$ , if excess if $N H_{4} C l$ is added before adding $N H_{4} O H$ , the concentration of:

N H_{4}^{+}

ions increases and

O H^{-}

ions decreases

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both

N H_{4}^{+}

ions and

O H^{-}

ions increases

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N H_{4}^{+}

ions decreases and

O H^{-}

ions increases

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both

N H_{4}^{+}

ions and

O H^{-}

ions decreases

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Solution

The correct option is A $N H_{4}^{+}$ ions increases and $O H^{-}$ ions decreases
From the law of Mass action, the dissociation of $N H_{4} O H$ takes place and we have,
$\frac{[N H_{4}^{+}] [O H^{-}]}{[N H_{4} O H]} = K$
Ammonium chloride, a strong electrolyte, ionises almost completely as follows:
$N H_{4} C l \leftrightarrow N H_{4}^{+} + C l^{-}$
So, if excess of $N H_{4} C l$ is added before adding $N H_{4} O H$ , the concentration of $N H_{4}^{+}$ ions is increased and consequently the concentration of $O H^{-}$ ions is decreased.

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Similar questions

Q. Assertion: On addition of

N H_{4} C l

N H_{4} O H, p H

decreases but remains greater than 7.
Reason: Addition of

⊝ N H_{4}

ion decreases ionisation of

N H_{4}

, thus [OH] decreases and also pH decreases.

Q. In III group precipitation

N H_{4} C l

is added before adding

N H_{4} O H

Q. The dissolution of ammonia gas in water does not obey Henry's law. On dissolving, a major portion o fammonia, molecules unite with

H_{2} O

to form

{N H}_{4} O H

molecules.

{N H}_{4} O H

again dissociates into

{N H}_{4}^{+}

and

{O H}^{-}

ions. In solution therefore, we have

{N H}_{3}

molecules,

{N H}_{4} O H

molecules and

{N H}_{4}^{+}

ions and the following equilibrium exist:

{N H}_{3} (g)

(pressure

P

and concentration

c

) Initially

⇌ {N H}_{3} (l) + H_{2} O ⇌ {N H}_{4} O H ⇌ {N H}_{4}^{+} + {O H}^{-}

Let

c_{1}

m o l / L

{N H}_{3}

pass in liquid state which on dissolution in water froms

c_{2}

m o l / L

{N H}_{4} O H

. The solution contains

c_{3}

m o l / L

{N H}_{4}^{+}

ions. The dissociation constant of

{N H}_{4} O H

can be given as:

Q. Assertion :On addition of

{N H}_{4} C l

{N H}_{4} O H

solution,

p H

decreases but remains greater than

7

. Reason: Addition of

{N H}_{4}^{+}

ion decreases ionisation of

{N H}_{4} O H

thus

[{O H}^{-}]

is decreased hence,

p H

decreases.

Q. In the reaction,

N H_{3 (a q)} + H_{2} O_{(l)} = N H_{4}^{+} (a q) + O H^{-} (a q)

the ammonium ions is the-

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In the dissociation of NH4OH, if excess if NH4Cl is added before adding NH4OH, the concentration of:

In the dissociation of $N H_{4} O H$ , if excess if $N H_{4} C l$ is added before adding $N H_{4} O H$ , the concentration of: