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Principles Related to Practical Chemistry · Question 3

NEET (UG) 2026MCQEasy📈 Topic in 25% papers+4−1
1

Phenolphthalein is used as an indicator for the titration of sodium hydroxide solution against a standard solution of oxalic acid. The colour change that is observed at an alkaline pH close to the equivalence point during this titration is :

  1. pink to colourless
  2. pinkish red to yellow
  3. colourless to pink
  4. yellow to pinkish red

Answer

(3) colourless to pink

Solution

In this titration NaOH (from the burette) is added to oxalic acid (in the flask) containing phenolphthalein.

In acidic medium phenolphthalein stays colourless; as per NCERT it changes colour in the pH range 8.2–10, so the first drop of excess alkali just past the equivalence point gives a pink colour.

∴ Colour change: colourless to pink

Answer: (3)

NEET (UG) 2026

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2

Two products X and Y are formed in the following reaction sequence. [figure] The suitable method that can be used for the separation of products X and Y is :

  1. Continuous extraction
  2. Differential extraction
  3. Sublimation
  4. Fractional distillation
NEET (UG) 2026
3

In a test tube containing a salt, a few drops of dilute H2SO4 was added, which gave colourless vapours having the smell of vinegar. The vapours turned the blue litmus paper red. Identify the correct anion from the following :

  1. Carbonate, CO32-
  2. Sulphide, S2-
  3. Acetate, CH3COO-
  4. Sulphate, SO42-
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4

In potash alum, the ratio of K+ and SO42- ions is

  1. 3 : 2
  2. 1 : 2
  3. 2 : 1
  4. 2 : 3
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5

Which one of the following reactions does NOT belong to "Lassaigne's test"?

  1. Na + X NaX
  2. 2CuO + C 2Cu + CO2
  3. Na + C + N NaCN
  4. 2Na + S Na2S
NEET (UG) 2025
6

Match List-I with List-II Choose the correct answer from the options given below:

  1. A-III, B-IV, C-I, D-II
  2. A-III, B-IV, C-II, D-I
  3. A-IV, B-III, C-I, D-II
  4. A-IV, B-III, C-II, D-I
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7

Match List-I with List-II Choose the correct answer from the options given below :

  1. A-III, B-II, C-IV, D-I
  2. A-III, B-II, C-I, D-IV
  3. A-III, B-IV, C-II, D-I
  4. A-III, B-IV, C-I, D-II
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8

On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

  1. Crystallization
  2. Sublimation
  3. Distillation
  4. Chromatography
NEET (UG) 2024
9

During the preparation of Mohr's salt solution (Ferrous ammonium sulphate), which of the following acid is added to prevent hydrolysis of Fe2+ ion?

  1. dilute hydrochloric acid
  2. concentrated sulphuric acid
  3. dilute nitric acid
  4. dilute sulphuric acid
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10

Given below are certain cations. Using inorganic qualitative analysis, arrange them in increasing group number from 0 to VI. Choose the correct answer from the options given below.

  1. B, A, D, C, E
  2. B, C, A, D, E
  3. E, C, D, B, A
  4. E, A, B, C, D
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11

Which indicator is used in the titration of sodium hydroxide against oxalic acid and what is the colour change at the end point?

  1. Phenolphthalein, pink to yellow
  2. Alkaline KMnO4, colourless to pink
  3. Phenolphthalein, colourless to pink
  4. Methyl orange, yellow to pinkish red colour
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