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Compounds that should not be used as primary standards in titrimetric analysis are: A. Na2Cr2O7 B. Oxalic acid C. NaOH D. FeSO4.6H2O E. Sodium tetraborate Choose the most appropriate answer from the options given below:

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

Correct answer: A, C and D only

Solution

NaOH, FeSO4.6H2O, and sodium tetraborate are not suitable as primary standards because they are hygroscopic, unstable, or do not have a consistent composition, which can lead to inaccuracies in titrimetric analysis.

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