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Consider the following statements regarding potassium hydrogen phthalate (KHP) and its use in the standardisation of NaOH solution: (A) KHP is preferred as a primary standard because it is non-hygroscopic and available in high purity. (B) KHP acts as a dibasic acid in this titration, so its equivalent weight is half of its molecular weight. (C) Methyl orange is the preferred indicator for this titration. (D) The pH a

Options

  1. A(A), (B) and (C) only
  2. B(A) and (B) only
  3. C(A), (C) and (D) only
  4. D(A) and (D) only

Correct answer

D. (A) and (D) only

Step-by-step solution

Statement (A) is correct: KHP is an excellent primary standard because it is solid, non-hygroscopic, stable, and can be obtained in highly pure form. Statement (B) is incorrect: KHP (potassium hydrogen phthalate) has only one replaceable acidic proton. It acts as a monobasic acid, so its equivalent weight is equal to its molecular weight. Statement (C) is incorrect: The titration is between a weak acid (KHP) and a strong base ( NaOH ). The equivalence point lies in the basic region, so phenolphthalein is the prefer

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