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:

Chemistry · Redox Reactions

JEE Main 2025 — 3 April, Evening Shift — Question 7

Compounds that should not be used as primary standards in titrimetric analysis are :

A. $\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$

B. Oxalic acid

C. NaOH

D. $\mathrm{FeSO}_{4} .6 \mathrm{H}_{2} \mathrm{O}$

E. Sodium tetraborate

Choose the most appropriate answer from the options given below:

Option A:
C, D and E only
Option B:
A, C and D only
Correct
Option C:
D and E only
Option D:
B and D only

Answer: B

Step-by-step solution

Compounds like $\mathrm{NaOH}, \mathrm{FeSO}_{4} \cdot 6 \mathrm{H}_{2} \mathrm{O}, \mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ are not suitable as primary standards in titrimetric

analysis because they are hydroscopic, unstable or difficult to obtain in a pure state.

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 3 April, Evening Shift
Subject: Chemistry
Chapter: Redox Reactions
Topic: n-Factor, Redox Titrations, Self Indicator & Miscellaneous Cases