Hydrogen peroxide oxidises $Fe(CN{)}_6{]}^{4-} to [Fe(CN{)}_6{]}^{3-}$ in acidic medium but reduces $\left[Fe\right(CN{)}_6{]}^{3-} to \left[Fe\right(CN{)}_6{]}^{4-}$ in alkaline medium. The other products formed are, respectively

• H₂O and (H₂O + OH^-)

• (H₂O + O₂) and H₂O

• (H₂O + O₂) and (H₂O + OH^-)

• H₂O and (H₂O + O₂)

How many faradays are required to reduce 1 mol of Cr₂O${}_7^{2-}$ to Cr³⁺ in acid medium?

• 2

• 3

• 5

• 6

Nitric acid can be obtained from ammonia via the formations of the intermediate compounds

• nitric oxide and nitrogen dioxide

• nitrogen and nitric oxide

• nitric oxide and dinitrogen pentoxide

• nitrogen and nitrous oxide

In the reaction

K₂Cr₂O₇ $\stackrel{∆}{\to }$ K₂CrO₄ + O₂ + (X), (X) is

• CrO₃

• C₂O₇

• Cr₂O₃

• CrO₄

What are the species (A) and (B) in the following

CrO₃ + H₂O → (A) $\stackrel{{\mathrm{OH}}^{-}}{\to }$ (B)

• H₂CrO₄, H₂Cr₂O₇

• H₂Cr₂O₇, Cr₂O₃

• CrO${}_4^{2-}$, Cr₂O${}_7^{2-}$

• H₂CrO₄, CrO${}_4^{2-}$

In the reaction,

2FeCl₃ + H₂S → 2FeCl₂ + 2HCl + S

The correct statement is

• FeCl₃ acts as an oxidising agent

• H₂S and FeCl₃ both act as an oxidising agent

• FeCl₃ get oxidised while H₂S get reduced

• H₂S acts as an oxidising agent

187.

When copper is treated with a certain concentration of nitric acid, nitric oxide and nitrogen dioxide are liberated in equal volumes according to the equation,

xCu + yHNO₃ → Cu(NO₃)₂ + NO + NO₂ + H₂O

The coefficients of x and y are respectively

• 2 and 3

• 2 and 6

• 1 and 3

• 3 and 8

The standard reduction potentials at 298 K for the following half reactions are given against each:

$$\begin{gathered} {\mathrm{Zn}}^{+}\left(\mathrm{aq}\right) +2{\mathrm{e}}^{-}\to \mathrm{Zn}\left(\mathrm{s}\right) {\mathrm{E}}^{°} = - 0.762 \mathrm{V} \\ {\mathrm{Cr}}^{3+} \left(\mathrm{aq}\right) + 3{\mathrm{e}}^{-} \to \mathrm{Cr}\left(\mathrm{s}\right) {\mathrm{E}}^{°} = - 0.7420\mathrm{V} \\ 2{\mathrm{H}}^{+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-} \to {\mathrm{H}}_2\left(\mathrm{g}\right) {\mathrm{E}}^{°} = 0.00\mathrm{V} \\ {\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right) + 3{\mathrm{e}}^{-} \to {\mathrm{Fe}}^{2+ }{\mathrm{E}}^{°} =+ 0.762 \mathrm{V} \end{gathered}$$

The strongest reducing agents is:

• Zn(s)

• Cr(s)

• H₂ (g)

• Fe²⁺ (aq)

The standard ${\mathrm{E}}_{\mathrm{red}}^{°}$ values of A, B  and C are +0.68 V, - 2.54 V,- 0.50 V respectively. The rder of their reducing power is

• A> B >C

• A> C > B

• C > B > A

• B > C > A

Oxidation potential of unimoles of calomel is

• + 0.25 V

• 0.00 V

• + 0.287 V

• -0.28 V