COMEDK 2025 Morning Shift | Redox Reactions Question 6 | Chemistry

The concentration and percentage purity of Oxalic acid can be determined by titration with $\mathrm{KMnO}_4$ in presence of dil. $\mathrm{H}_2 \mathrm{SO}_4$. Instead of dil. $\mathrm{H}_2 \mathrm{SO}_4$, dil HCl cannot be used because

HCl can also reduce $\mathrm{MnO}_4^{-}$to $\mathrm{Mn}^{2+}$

HCl can also provide $\mathrm{H}^{+}$ions in addition to $\mathrm{H}^{+}$ions from Oxalic acid.

HCl can also oxidise Oxalic acid to $\mathrm{CO}_2$ and $\mathrm{H}_2 \mathrm{O}$.

Oxalic acid oxidises HCl to $\mathrm{Cl}_2$.

COMEDK 2025 Morning Shift

MCQ (Single Correct Answer)

-0

Which one of the following options represents the decreasing order of oxidation number of the central atom in:

$$\mathrm{Cr}_2 \mathrm{O}_7^{2-}, \mathrm{Cr} \mathrm{O}_2^{-}, \mathrm{MnO}_4^{-}, \mathrm{BrO}_3^{-}$$

$\mathrm{CrO}_2^{-}>\mathrm{BrO}_3^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{MnO}_4^{-}$

$\mathrm{MnO}_4^{-}>\mathrm{CrO}_2^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{BrO}_3^{-}$

$\mathrm{BrO}_3^{-}>\mathrm{CrO}_2^{-}>\mathrm{MnO}_4^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}$

$\mathrm{MnO}_4^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{BrO}_3^{-}>\mathrm{CrO}_2^{-}$

COMEDK 2024 Evening Shift

MCQ (Single Correct Answer)

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In the redox reaction between $$\mathrm{Cr}_2 \mathrm{O}_7^{2-} / \mathrm{H}^{+}$$ and sulphite ion, what is the number of moles of electrons involved in producing 3.0 moles of the oxidised product?

COMEDK 2024 Afternoon Shift

MCQ (Single Correct Answer)

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In the reaction,

$$2 \mathrm{~S}_2 \mathrm{O}_3^{2-}+\mathrm{I}_2 \rightarrow \mathrm{S}_4 \mathrm{O}_6^{2-}+2 \mathrm{I}^{-}$$

$$\mathrm{S}_2 \mathrm{O}_3^{2-}$$ gets oxidised to $$\mathrm{S}_4 \mathrm{O}_6^{2-}$$

$$\mathrm{I_2}$$ is a reducing agent

$$\mathrm{I}_2$$ get oxidised to $$\mathrm{I}^{-}$$

$$\mathrm{S}_2 \mathrm{O}_3^{2-}$$ gets reduced to $$\mathrm{S}_4 \mathrm{O}_6^{2-}$$

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