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Saturday, 31 October

JEE Main 2023 · ChemistryNumerical answerNumerical valueMediumConceptual

JEE Main 8 April 2023, Shift 1, Chemistry Q86

Question 86 of 90 in this shift, Chemistry question 26 of 30, Section B.

The titration curve of weak acid vs. strong base with phenolphthalein as indictor) is shown below. The Kphenolphthalein=4×10−10\mathrm{K_{phenolphthalein}} = 4\times10^{-10}. Given: log⁡2=0.3\log 2 = 0.3 [graph] The number of following statement/s which is/are correct about phenolphthalein is ________ A. It can be used as an indicator for the titration of weak acid with weak base. B. It begins to change colour at pH = 8.4 C. It is a weak organic base D. It is colourless in acidic medium

The figure, in words

Titration curve: pH (y axis, ticks 0, 6, 8, 10, 12) vs VNaOHV_{NaOH} (x axis, ticks 5, 10, 15, 20, 25). Curve starts near pH 2-3, rises to about 6 (buffer region), then rises sharply near V = 10 (dashed vertical at 10) through pH 8-9 (dashed horizontal at pH 9) to about 11, then flattens slowly to about 13 by V = 25.

Official answer

2

NTA final key.

Chapter
Equilibrium
Topic
pH and Buffers
Idea tested
pH of Acid-Base Indicators

Same topic in other shifts

All pH and Buffers questions
  1. 2 Apr 2026, Shift 2 · Q52The first and second ionization constants of a weak dibasic acid H2A\mathrm{H_2A} are 8.1×10−88.1 \times 10^{-8} and 1.0×10−131.0 \times 10^{-13}…HardSingle correct
  2. 2 Apr 2026, Shift 2 · Q56At 25°C, 20.0 mL of 0.2 M weak monoprotic acid HX is titrated against 0.2 M NaOH. The pH of the solution (a) at the start of the titration…MediumSingle correct
  3. 4 Apr 2026, Shift 1 · Q74The pH of a solution obtained by mixing 55 mL of 0.10.1 M NH4OH\mathrm{NH_4OH} solution with 250250 mL of 0.10.1 M NH4Cl\mathrm{NH_4Cl} solution…MediumNumerical value
  4. 4 Apr 2026, Shift 2 · Q5520 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…EasySingle correct
  5. 5 Apr 2026, Shift 1 · Q56Arrange the following resultant mixtures in increasing order of their pH values A. 10 mL 0.2 M Ca(OH)2\mathrm{Ca(OH)_2} + 25 mL 0.1 M HCl B. 10…MediumOther
  6. 6 Apr 2026, Shift 2 · Q56Given is a concentrated solution of a weak electrolyte AxBy\mathrm{A_xB_y} of concentration 'c' and dissociation constant 'K'. The degree of…HardSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.