At T ( K ) , if the ionization constants of HCOOH and HCN are 2 . 0 × 10 - 4 and 5 . 0 × 10 - 9 , respectively, the ionization constants of the corresponding conjugate bases, respectively, are

5 . 0 × 10 - 11 , 2 . 0 × 10 - 6

2 . 0 × 10 - 6 , 5 . 0 × 10 - 11

2 . 0 × 10 - 4 , 5 . 0 × 10 - 9

5 . 0 × 10 - 9 , 2 . 0 × 10 - 4

HARD

Earn 100

(i) Calculate the ratio of the $pH$ of a solution containing $1 mol$ of ${CH}_{3} COONa$ and $1 mol$ of $HCl$ per litre and of another solution containing $1 mol$ of ${CH}_{3} COONa$ and $1 mol$ of ${CH}_{3} COOH$ per litre.
(ii) A $0.1 M$ solution of a weak acid $HA$ is $1 %$ dissociated at $298 K$ . What is its $K_{a}$ ? What will be the new degree of dissociation of $HA$ and $pH$ when $0.2 M$ of $NaA$ is added to it?

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Important Questions on Equilibrium

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Ostwald's dilution law is applicable only for

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

0.004 M

{Na}_{2} {SO}_{4}

is isotonic with

0.01 M

glucose solution. The degree of dissociation of

{Na}_{2} {SO}_{4}

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Assuming that

Ba (OH)_{2}

is completely ionised in aqueous solution under the given conditions the concentration of

H_{3} O^{+}

ions in

0.005 M

aqueous solution of

Ba (OH)_{2}

298 K

is _________

\times 10^{- 12} mol L^{- 1} .

(Nearest integer)

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The

pH

0.1 M

solution of acetic acid will be [degree of dissociation of acetic acid is

0.0132

]

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

An aqueous solution in which the

H^{+}

ion concentration is greater than

10^{- 7} M

is said to be

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

K_{a}

values for acids

H_{2} {SO}_{3}, {HNO}_{2}, {CH}_{3} COOH

and

HCN

are respectively

1.3 \times 10^{- 2}, 4 \times 10^{- 4}, 1.8 \times 10^{- 5}

and

4 \times 10^{- 10},

which of the above acids produces stronger conjugate base in aqueous solution?

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The acid dissociation constants of methanoic acid, monochloroethanoic acid and ethanoic acid are

K_{1}, K_{2}

and

K_{3}

respectively. If

K_{2} > K_{1} > K_{3}

, then

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Match the following

Acid		Ionization constant, $K_{a}$
A)	Formic acid	I)	$4.9 \times 10^{- 10}$
B)	Niacin	II)	$1.5 \times 10^{- 5}$
C)	Hypochlorous acid	III)	$1.8 \times 10^{- 4}$
D)	Hydrocyanic acid	IV)	$3 \times 10^{- 8}$

The correct match is

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The

pH

of an aqueous solution of

10^{- 8} MHCl

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

$0.01$ moles of a weak acid $HA (K_{a} = 2.0 \times 10^{- 6})$ is dissolved in $1.0 L$ of $0.1 M HCl$ solution. The degree of dissociation of $HA$ is __________ $\times 10^{- 5}$ (Round off to the Nearest Integer). [Neglect volume change on adding $HA$ and assume degree of dissociation $< < 1$ ]

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The degree of dissociation of

0.1 M

acid

HA

5 % .

The value of

K_{c}

HA

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The degree of dissociation of

0.1 N {CH}_{3} COOH

is (given

K_{a} = 1 \times 10^{- 5}

) approximately _________

HARD

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Acetylsalicylic acid has

{pK}_{a}

value

3.5 .

The

pH

of gastric juice in human stomach is

2 - 3

and the pH in the small intestine is approximately

7.4 .

Then acetylsalicylic acid will be

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

{CH}_{3} COOH

1 %

ionised in its aqueous solution of

0.1 M

strength. Its

pOH

will be

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Match the following

List-1 Acid		List-2 Ka(ionization constant)
A)	$HCN$	I)	$6.8 \times 10^{- 4}$
B)	$H_{2} C_{2} O_{4}$	II)	$8.9 \times 10^{- 8}$
C)	$H_{2} S$	III)	$4.9 \times 10^{- 10}$
D)	Niacin	IV)	$5.6 \times 10^{- 2}$
		V)	$1.5 \times 10^{- 5}$

The correct match is

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$ .

Assertion $A$ :Phenolphthalein is a $pH$ dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium

Reason $R$ : Phenolphthalein is a weak acid. It doesn't dissociate in basic medium.

In the light of the above statements, choose the most appropriate answer from the options given below

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The

pH

0.1 M

acetic acid solution is closest to [Dissociation constant of the acid,

K_{a} = 1.8 \times 10^{- 5}

]

HARD

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

Sulphurous acid

(H_{2} {SO}_{3})

has

{Ka}_{1} = 1.7 \times 10^{- 2}

and

{Ka}_{2} = 6.4 \times 10^{- 8} .

The

pH

0.588 M H_{2} {SO}_{3}

is____________

(

Round off to the Nearest Integer

)

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

T (K)

, if the ionization constants of

HCOOH

and

HCN

are

2.0 \times 10^{- 4}

and

5.0 \times 10^{- 9}

, respectively, the ionization constants of the corresponding conjugate bases, respectively, are

EASY

Chemistry>Physical Chemistry>Equilibrium>Ionization of Weak Acids and Weak Bases

The degree of dissociation of $0 .1 mol L^{- 1}$ acetic acid in water is

( $K$ of acetic acid is $10^{- 5}$ )

Important Questions on Equilibrium

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