Subject: Inorganic Chemistry · Chapter: Analytical Chemistry · Topic: Analytical Chemistry – General · Exam: CSIR-NET JUNE 2019 · Marks: 2 · Difficulty: Medium
The role of $\mathrm{H_3PO_4}$ in the estimation of Fe (II) with $\mathrm{K_2Cr_2O_7}$ using diphenylamine sulphonate as indicator is to
(a)avoid aerial oxidation of Fe (II)
(b)reduce the electrode potential of $\mathrm{Fe}^{3+}-\mathrm{Fe}^{3+}$
(c)stabilize the indicator
(d)stabilize $\mathrm{K_2Cr_2O_7}$
Answer
Answer (as printed): B
Explanation
$\mathrm{H_3PO_4}$ is used in the estimation of Fe(II) with $\mathrm{K_2Cr_2O_7}$ using diphenylamine sulphonate as indictor to reduce the electrode potential for the $\mathrm{Fe^{3+} \rightarrow Fe^{2+}}$ reaction by stabilising the ferric ion.