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Compounds that should not be used as primary standards in titrimetric analysis are : A. Na ₂ Cr ₂ O ₇ B. Oxalic acid C. NaOH D. FeSO ₄ 6 H ₂ O E. Sodium tetraborate Choose the most appropriate answer from the options given below:

Options

  1. AB and D Only
  2. BD and E Only
  3. CC, D and E Only
  4. DA, C and D Only

Correct answer

D. A, C and D Only

Step-by-step solution

The primary standard is a highly pure stable compound with a known exact composition that can be accurately weighed and dissolved to creat a solution of known concentration. NaOH is hygroscopic and can't be used. FeSO ₄ 6 H ₂ O is unstable and can be easily oxidised. Na ₂ Cr ₂ O ₇ is hygroscopic and can't be used.

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