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pH of a buffer formed by mixing or by partly neutralising a weak acid or base

This type of question, asked 6 times: 26 Jun 2022, 25 Jan 2023, 13 Apr 2023, 7 Apr 2025, 4 Apr 2026 S1, 4 Apr 2026 S2. All 6 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    26 Jun 2022

    53
    50 mL50\text{ }mL of 0.1MCH3COOH0.1MCH_{3}COOH is being titrated against 0.1MNaOH0.1MNaOH. When 25 mL25\text{ }mL of NaOHNaOH has been added, the pHpH of the solution will be ×10−2\times10^{- 2}. (Nearest integer) (Given:  pKa(CH3COOH)=4.76)\left. \ pK_{a}\left( CH_{3}COOH \right)= 4.76 \right) log⁡2=0.30\log2 = 0.30 log⁡3=0.48\log3 = 0.48
    log⁡5=0.69\log5 = 0.69
    log⁡7=0.84\log7 = 0.84
    log⁡11=1.04\log11 = 1.04

  2. Question 2

    25 Jan 2023

    60
    A litre of buffer solution contains 0.1 mole of each of NH3NH_{3} and NH4ClNH_{4}Cl. On the addition of 0.02 mole of HClHCl by dissolving gaseous HClHCl, the pHpH of the solution is found to be [Given: pKb(NH3)=4.745pK_{b}\left( NH_{3} \right)= 4.745
    log⁡2=0.301log⁡3=0.477T=298 K]\begin{matrix} & \log2 = 0.301 \\ & \log3 = 0.477 \\ & T= 298\text{ }K\rbrack \end{matrix}

  3. Question 3

    13 Apr 2023

    146
    20 mL20\text{ }mL of 0.1MNaOH0.1MNaOH is added to 50 mL50\text{ }mL of 0.1M0.1M acetic acid solution. The pHpH of the resulting solution is____ ×10−2\times10^{- 2} (Nearest integer) Given: pKa(CH3COOH)=4.76pKa\left( CH_{3}COOH \right)= 4.76
    log⁡2=0.30\log2 = 0.30
    log⁡3=0.48\log3 = 0.48

  4. Question 4

    7 Apr 2025

    121
    One litre buffer solution was prepared by adding 0.10 mol each of NH3{NH}_{3} and NH4Cl{NH}_{4}Cl in deionised water. The change in pH on addition of 0.05 mol of HCl to the above solution is ____\_\_\_\_ ×10−2\times 10^{- 2}. (Nearest integer) (Given : pKb{pK}_{b} of NH3=4.745{NH}_{3} = 4.745 and log⁡103=0.477\log_{10}3 = 0.477 ).

  5. Question 5

    4 Apr 2026 S1

    49
    The pH a solution obtained by mixing 5 mL of 0.1MNH4OH0.1M{NH}_{4}OH solution with 250 mL of 0.1 M NH4Cl{NH}_{4}Cl solution is ____\_\_\_\_ ×10−2\times 10^{- 2}. (Nearest integer) Given : pKb(NH4OH)=4.74{pK}_{b}\left( {NH}_{4}OH \right) = 4.74
    log⁡2=0.30\log2 = 0.30
    log⁡3=0.48\log3 = 0.48
    log⁡5=0.70\log5 = 0.70

  6. Question 6

    4 Apr 2026 S2

    30
    20 mL of a solution of acetic acid required 28.4 mL of 0.1 M NaOH for its neutralization. A solution (X) was prepared by mixing 20 mL of the above acetic acid and 14.2 mL of 0.1 M NaOH solution. What is the pH of the solution (X) ? (pKa\left( pK_{a} \right. value of acetic acid is 4.75).

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