Potassium dichromate and potassium permanganate — NEET & JEE Questions

Question 1 · difficulty L1 · recall

In acidic solution, potassium permanganate is a strong

• A. oxidising agent
• B. reducing agent only
• C. acid-base indicator only
• D. precipitating agent only

Question 2 · difficulty L2 · understanding

A paper dipped in a dil. $\mathrm{H}_2 \mathrm{SO}_4$ solution of ' $X$ ' upon treatment with $\mathrm{SO}_2$ gas turns into green. The compound ' $X$ ' is :

• A. $\mathrm{KI-strach}$
• B. $\mathrm{KMnO}_4$
• C. $\mathrm{Pb}\left(\mathrm{CH}_3 \mathrm{COO}\right)_2$
• D. $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$

Question 3 · difficulty L2 · understanding

Which of the following sets includes all the species that will change the orange colour of $\mathrm{K_2Cr_2O_7}$ in acidic medium?

• A. $\mathrm{Fe^{2+},\ Sn^{2+},\ I^-,\ S^{2-}}$
• B. $\mathrm{S^{2-},\ Fe^{3+},\ I^-,\ C_2O_4^{2-}}$
• C. $\mathrm{Fe^{2+},\ NO_2^-,\ SO_2,\ Sn^{4+}}$
• D. $\mathrm{Fe^{3+},\ SO_4^{2-},\ S^{2-},\ Sn^{4+}}$

Question 4 · difficulty L2 · understanding

$\mathrm{MnO}_4{ }^{2-}$, in acidic medium, disproportionates to :

• A. $\mathrm{MnO}_4^{-}$and MnO
• B. $\mathrm{MnO}_4^{-}$and $\mathrm{MnO}_2$
• C. $\mathrm{Mn}_2 \mathrm{O}_7$ and $\mathrm{MnO}_2$
• D. $\mathrm{Mn}_2 \mathrm{O}_7$ and MnO

Question 5 · difficulty L2 · understanding

Preparation of potassium permanganate from $\mathrm{MnO}_2$ involves two step process in which the 1st step is a reaction with KOH and $\mathrm{KNO}_3$ to produce

• A. $\mathrm{K}_3 \mathrm{MnO}_4$
• B. $\mathrm{K}_4\left[\mathrm{Mn}(\mathrm{OH})_6\right]$
• C. $\mathrm{K}_2 \mathrm{MnO}_4$
• D. $\mathrm{KMnO}_4$

Question 6 · difficulty L2 · understanding

Match List - I with List - II List - I List - II (A) Bronze (I) Cu, Ni (B) Brass (II) Fe, Cr, Ni, C (C) UK silver coin (III) Cu, Zn (D) Stainless steel (IV) Cu, Sn Choose the correct answer from the options given below :

• A. (A)-(IV), (B)-(II), (C)-(III), (D)-(I)
• B. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
• C. (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
• D. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)

Question 7 · difficulty L2 · understanding

Consider the following reactions $$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7 \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{KOH}}[\mathrm{~A}] \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{H}_2 \mathrm{SO}_4}[\mathrm{~B}]+\mathrm{K}_2 \mathrm{SO}_4$$ The products $[A]$ and $[B]$, respectively are :

• A. $\mathrm{K}_2 \mathrm{Cr}(\mathrm{OH})_6$ and $\mathrm{Cr}_2 \mathrm{O}_3$
• B. $\mathrm{K}_2 \mathrm{CrO}_4$ and $\mathrm{Cr}_2 \mathrm{O}_3$
• C. $\mathrm{K}_2 \mathrm{CrO}_4$ and $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$
• D. $\mathrm{K}_2 \mathrm{CrO}_4$ and $\mathrm{CrO}$

Question 8 · difficulty L2 · understanding

While preparing crystals of Mohr's salt, dil $$\mathrm{H}_2 \mathrm{SO}_4$$ is added to a mixture of ferrous sulphate and ammonium sulphate, before dissolving this mixture in water, dil $$\mathrm{H_2SO_4}$$ is added here to :

• A. prevent the hydrolysis of ferrous sulphate
• B. prevent the hydrolysis of ammonium sulphate
• C. increase the rate of formation of crystals
• D. make the medium strongly acidic

Question 9 · difficulty L2 · understanding

Choose the correct statements from the following A. $$\mathrm{Mn}_2 \mathrm{O}_7$$ is an oil at room temperature B. $$\mathrm{V}_2 \mathrm{O}_4$$ reacts with acid to give $$\mathrm{VO}_2{ }^{2+}$$ C. $$\mathrm{CrO}$$ is a basic oxide D. $$\mathrm{V}_2 \mathrm{O}_5$$ does not react with acid Choose the correct answer from the options given below :

• A. A, B and D only
• B. A, B and C only
• C. A and C only
• D. B and C only

Question 10 · difficulty L2 · understanding

The metals that are employed in the battery industries are A. $$\mathrm{Fe}$$ B. $$\mathrm{Mn}$$ C. $$\mathrm{Ni}$$ D. $$\mathrm{Cr}$$ E. $$\mathrm{Cd}$$ Choose the correct answer from the options given below:

• A. A, B, C, D and E
• B. A, B, C and D only
• C. B, D and E only
• D. B, C and E only