1
COMEDK 2025 Morning Shift
MCQ (Single Correct Answer)
+1
-0
Choose the correct statement.
A
Calcium and Magnesium metals are manufactured by electrolysis of aqueous solutions of their salts
B
The oxo-anion $\mathrm{ClO}_3^{-}$does not undergo disproportionation reaction
C
Nitride ion $\mathrm{N}^{-3}$ cannot act as an oxidising agent
D
In alkaline medium the reduction of $\mathrm{MnO}_4^{-}$ion involves gain of 5 electrons
2
COMEDK 2025 Morning Shift
MCQ (Single Correct Answer)
+1
-0
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
A
HCl can also reduce $\mathrm{MnO}_4^{-}$to $\mathrm{Mn}^{2+}$
B
HCl can also provide $\mathrm{H}^{+}$ions in addition to $\mathrm{H}^{+}$ions from Oxalic acid.
C
HCl can also oxidise Oxalic acid to $\mathrm{CO}_2$ and $\mathrm{H}_2 \mathrm{O}$.
D
Oxalic acid oxidises HCl to $\mathrm{Cl}_2$.
3
COMEDK 2025 Morning Shift
MCQ (Single Correct Answer)
+1
-0

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

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

A
$\mathrm{CrO}_2^{-}>\mathrm{BrO}_3^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{MnO}_4^{-}$
B
$\mathrm{MnO}_4^{-}>\mathrm{CrO}_2^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{BrO}_3^{-}$
C
$\mathrm{BrO}_3^{-}>\mathrm{CrO}_2^{-}>\mathrm{MnO}_4^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}$
D
$\mathrm{MnO}_4^{-}>\mathrm{Cr}_2 \mathrm{O}_7^{2-}>\mathrm{BrO}_3^{-}>\mathrm{CrO}_2^{-}$
4
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

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?

A
8
B
2
C
3
D
6
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