pH, Buffer and Indicator

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JEE Advanced 2015

Comprehension Passage

100 mL

1.0 M

HCl

was mixed with

100 mL

1.0 M

NaOH

in an insulated beaker at constant pressure, a temperature increase of

5.7^{\circ} C

was measured for the beaker and its contents. (Expt-1). Because the enthalpy of neutralisation of a strong acid with a strong base is a constant (

- 57.0 kJ mol^{- 1}

), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt-2),

100 mL

2.0 M

acetic acid (

K_{a} = 2.0 \times 1 0^{- 5}

) was mixed with

100 mL

1.0 M

NaOH

(under identical conditions to (Expt-1)) where a temperature rise of

5.6^{\circ} C

was measured. (Consider heat capacity of all solutions as

4.2 J g^{- 1} K^{- 1}

and density of all solutions as

1.0 g mL^{- 1}

)

Question 1:

Enthalpy of dissociation (in $kJ mol^{- 1}$ ) of acetic acid obtained from the Expt-2 is

The $pH$ of the solution after Expt-2

A solution of 0.1 M weak base (B) is titrated with 0.1 M of a strong acid (HA). The variation of pH of the solution with the volume of HA added is shown in the figure below. What is the $p K_{b}$ of the base? The neutralization reaction is given by $B + HA \to BH^{+} + A^{-}$ .

JEE Advanced 2022

LEVELJEE Advanced

A solution is prepared by mixing $0.01 mol$ each of $H_{2} CO_{3}$ , $NaHCO_{3}$ , $Na_{2} CO_{3}$ , and $NaOH$ in $100 mL$ of water. pH of the resulting solution is ______. [Given : $p K_{a 1}$ and $p K_{a 2}$ of $H_{2} CO_{3}$ are $6.37$ and $10.32$ , respectively ; $lo g 2 = 0.30$ ]

JEE Main 2019

LEVELJEE Main

In an acid-base titration, 0.1 M HCl solution was added to the NaOH solution of unknown strength. Which of the following correctly shows the change of pH of the titration mixture in this experiment?

The $OH^{-}$ concentration in a mixture of $5.0 mL$ of $0.0504 M$ $NH_{4} Cl$ and $2 mL$ of $0.0210 M$ $NH_{3}$ solution is $x \times 1 0^{- 6} M$ . The value of $x$ is ......... . (Nearest integer) [Given, $K_{w} = 1 \times 1 0^{- 14}$ and $K_{b} = 1.8 \times 1 0^{- 5}$ ]

JEE Main 2021

LEVELJEE Main

Given below are two statements. Statement I In the titration between strong acid and weak base methyl orange is suitable as an indicator. Statement II For titration of acetic acid with NaOH phenolphthalein is not a suitable indicator. In the light of the above statements, choose the most appropriate answer from the options given below.

(A)

Statement I is false but statement II is true.

(B)

Statement I is true but statement II is false.

(C)

Both statement I and statement II are true.

(D)

Both statement I and statement II are false.

JEE Main 2020

LEVELJEE Main

The strength of an aqueous $NaOH$ solution is most accurately determined by titrating : (Note : consider that an appropriate indicator is used)

(A)

Aq.

NaOH

in a volumetric flask and concentrated

H_{2} SO_{4}

in a conical flask

(B)

Aq.

NaOH

in a pipette and aqueous oxalic acid in a burette

(C)

Aq.

NaOH

in a burette and aqueous oxalic acid in a conical flask

(D)

Aq.

NaOH

in a burette and concentrated

H_{2} SO_{4}

in a conical flask

JEE Main 2020

LEVELJEE Main

An acidic buffer is obtained on mixing

(A)

100 mL of 0.1 M

CH_{3} COOH

and 100 mL of 0.1 M NaOH

(B)

100 mL of 0.1 M HCl and 200 mL of 0.1 M NaCl

(C)

100 mL of 0.1 M

CH_{3} COOH

and 200 mL of 0.1 M NaOH

(D)

100 mL of 0.1 M HCl and 200 mL of 0.1 M

CH_{3} COONa

LEVELJEE Main

Which one of the following statements is not true?

(A)

The conjugate base of

H_{2} PO_{4}^{-}

HPO_{4}^{2 -}

(B)

pH + pOH = 14

for all aqueous solutions

(C)

The pH of

1 \times 1 0^{- 8} M HCl

is 8

(D)

96,500 C of electricity when passed through a

CuSO_{4}

solution deposits 1g equivalent of copper at the cathode

JEE Main 2020

LEVELJEE Main

For the following Assertion and Reason, the correct option is Assertion (A) The pH of water increases with increase in temperature. Reason (R) The dissociation of water into $H^{+}$ and $OH^{-}$ is an exothermic reaction.

(A)

Assertion is not true, but Reason is true.

(B)

Both assertion and Reason are true and the Reason is the correct explanation for the Assertion.

(C)

Both Assertion and Reason are false.

(D)

Both Assertion and Reason are true, but the Reason is not the correct explanation for the Assertion.

JEE Main 2020

LEVELJEE Advanced

A soft drink was bottled with a partial pressure of $CO_{2}$ of 3 bar over the liquid at room temperature. The partial pressure of $CO_{2}$ over the solution approaches a value of 30 bar when 44 g of $CO_{2}$ is dissolved in 1 kg of water at room temperature. The approximate pH of the soft drink is ...... $\times 1 0^{- 1}$ . (First dissociation constant of $H_{2} CO_{3} = 4.0 \times 1 0^{- 7}$ ) $lo g 2 = 0.3$ ; density of the soft drink $= 1 g mL^{- 1}$ )

JEE Main 2020

LEVELJEE Advanced

3 g of acetic acid is added to 250 mL of 0.1 M HCl and the solution made up to 500 mL. To 20 mL of this solution $\frac{1}{2}$ mL of 5 M NaOH is added. The pH of the solution is ………… [Given : $p K_{a}$ of acetic acid = 4.75, molar mass of acetic acid = 60 g/mol, $lo g 3 = 0.4771$ ] Neglect any changes in volume.

JEE Main 2020

LEVELJEE Main

100 mL of 0.1M HCl is taken is a beaker and to it 100 mL of 0.1 M NaOH is added in steps of 2 mL and the pH continuously measured. Which of the following graphs correctly depicts the change in pH?

20 mL of 0.1 M $H_{2} SO_{4}$ solution is added to 30 mL of 0.2 M $NH_{4} OH$ solution. The pH of the resultant mixture is [ $pK_{b}$ of $NH_{4} OH = 4.7$ ]

The $p K_{a}$ of a weak acid (HA) is $4.5$ . The pOH of an aqueous buffered solution of HA in which $50%$ of the acid ionised is

(A)

4.5

(B)

2.5

(C)

9.5

(D)

7.0

JEE Main 2014

LEVELJEE Main

How many litres of water must be added to 1 L of an aqueous solution of HCl with a pH of 1 to create an aqueous solution with pH of 2?

The pH of a solution obtained by mixing $50 mL$ of $1 M$ HCl and $30 mL$ of $1 M$ NaOH is $x \times 1 0^{- 4}$ . The value of $x$ is ......... (Nearest integer) [ $lo g 2.5 = 0.3979$ ]

JEE Main 2020

LEVELJEE Main

Two solutions, $A$ and $B$ , each of $100 L$ was made by dissolving $4 g$ of $NaOH$ and $9.8 g$ of $H_{2} SO_{4}$ in water, respectively. The pH of the resultant solution obtained from mixing $40 L$ of solution $A$ and $10 L$ of solution $B$ is ……… .

JEE Main 2018

LEVELJEE Main

An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?

(A)

Base: Weak, Acid: Strong, End point: Colourless to pink

(B)

Base: Strong, Acid: Strong, End point: Pinkish red to yellow

(C)

Base: Weak, Acid: Strong, End point: Yellow to pinkish red

(D)

Base: Strong, Acid: Strong, End point: Pink to colourless

JEE Main 2021

LEVELJEE Main

In order to prepare a buffer solution of pH 5.74, sodium acetate is added to acetic acid. If the concentration of acetic acid in the buffer is 1.0 M, the concentration of sodium acetate in the buffer is ………… M. (Round off to the nearest integer). [Given : $p K_{a}$ (acetic acid) = 4.74]

JEE Main 2021

LEVELJEE Advanced

Sulphurous acid ( $H_{2} SO_{3}$ ) has $K_{a_{1}} = 1.7 \times 1 0^{- 2}$ and $K_{a_{2}} = 6.4 \times 1 0^{- 8}$ . The pH of $0.588 M$ is …… (Round off to the nearest integer)

LEVELJEE Main

Hydrogen ion concentration in mol/L in a solution of $pH = 5.4$ will be

(A)

3.98 \times 1 0^{- 6}

(B)

3.68 \times 1 0^{- 6}

(C)

3.88 \times 1 0^{6}

(D)

3.98 \times 1 0^{8}

LEVELJEE Main

An aqueous solution of 1M NaCl and 1M HCl is

(A)

not a buffer but pH < 7

(B)

not a buffer but pH > 7

Consider the following statements. I. The pH of a mixture containing 400 mL of 0.1 M $H_{2} S O_{4}$ and 400 mL of 0.1 M NaOH will be approximately 1.3. II. Ionic product of water is temperature dependent. III. A monobasic acid with $K_{a} = 1 0^{- 5}$ has a pH = 5. The degree of dissociation of this acid is 50%. IV. The Le-Chatelier's principle is not applicable to common-ion effect. The correct statements are

Comprehension Passage

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Enthalpy of dissociation (in kJ mol−1) of acetic acid obtained from the Expt-2 is

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The pH of the solution after Expt-2

In an acid-base titration, 0.1 M HCl solution was added to the NaOH solution of unknown strength. Which of the following correctly shows the change of pH of the titration mixture in this experiment?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The strength of an aqueous NaOH solution is most accurately determined by titrating : (Note : consider that an appropriate indicator is used)

An acidic buffer is obtained on mixing

Which one of the following statements is not true?

100 mL of 0.1M HCl is taken is a beaker and to it 100 mL of 0.1 M NaOH is added in steps of 2 mL and the pH continuously measured. Which of the following graphs correctly depicts the change in pH?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } 20 mL of 0.1 M H2​SO4​ solution is added to 30 mL of 0.2 M NH4​OH solution. The pH of the resultant mixture is [pKb​ of NH4​OH=4.7]

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The pKa​ of a weak acid (HA) is 4.5. The pOH of an aqueous buffered solution of HA in which 50% of the acid ionised is

How many litres of water must be added to 1 L of an aqueous solution of HCl with a pH of 1 to create an aqueous solution with pH of 2?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The pH of a solution obtained by mixing 50 mL of 1 M HCl and 30 mL of 1 M NaOH is x×10−4. The value of x is ......... (Nearest integer) [log2.5=0.3979]

An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Sulphurous acid (H2​SO3​) has Ka1​​=1.7×10−2 and Ka2​​=6.4×10−8. The pH of 0.588 M is …… (Round off to the nearest integer)

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Hydrogen ion concentration in mol/L in a solution of pH=5.4 will be

An aqueous solution of 1M NaCl and 1M HCl is

Enthalpy of dissociation (in $kJ mol^{- 1}$ ) of acetic acid obtained from the Expt-2 is

The $pH$ of the solution after Expt-2

The strength of an aqueous $NaOH$ solution is most accurately determined by titrating : (Note : consider that an appropriate indicator is used)

20 mL of 0.1 M $H_{2} SO_{4}$ solution is added to 30 mL of 0.2 M $NH_{4} OH$ solution. The pH of the resultant mixture is [ $pK_{b}$ of $NH_{4} OH = 4.7$ ]

The $p K_{a}$ of a weak acid (HA) is $4.5$ . The pOH of an aqueous buffered solution of HA in which $50%$ of the acid ionised is

The pH of a solution obtained by mixing $50 mL$ of $1 M$ HCl and $30 mL$ of $1 M$ NaOH is $x \times 1 0^{- 4}$ . The value of $x$ is ......... (Nearest integer) [ $lo g 2.5 = 0.3979$ ]

Sulphurous acid ( $H_{2} SO_{3}$ ) has $K_{a_{1}} = 1.7 \times 1 0^{- 2}$ and $K_{a_{2}} = 6.4 \times 1 0^{- 8}$ . The pH of $0.588 M$ is …… (Round off to the nearest integer)

Hydrogen ion concentration in mol/L in a solution of $pH = 5.4$ will be