Redox reactions play a pivotal role in chemistry and biology. The values of standard redox potential $$\left(\mathrm{E}^{\circ}\right)$$ of two half-cell reactions decide which way the reaction is expected to proceed. A simple example is a Daniel cell in which zinc goes into solution and copper gets deposited. Given below are a set of half-cell reactions (acidic medium) along with their $$\mathrm{E}^{\circ}$$ (V with respect to normal hydrogen electrode) values. Using this data obtain the correct explanations.

$$\begin{array}{ll} \mathrm{I}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{I}^{-} & \mathrm{E}^{\mathrm{o}}=0.54 \\ \mathrm{Cl}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cl}^{-} & \mathrm{E}^{\mathrm{o}}=1.36 \\ \mathrm{Mn}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+} & \mathrm{E}^{\mathrm{o}}=1.50 \\ \mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+} & \mathrm{E}^{\mathrm{o}}=0.77 \\ \mathrm{O}_{2}+4 \mathrm{H}^{+}+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O} & \mathrm{E}^{\mathrm{o}}=1.23 \end{array}$$

Among the following, identify the correct statement.

Redox reactions play a pivotal role in chemistry and biology. The values of standard redox potential $$\left(\mathrm{E}^{\circ}\right)$$ of two half-cell reactions decide which way the reaction is expected to proceed. A simple example is a Daniel cell in which zinc goes into solution and copper gets deposited. Given below are a set of half-cell reactions (acidic medium) along with their $$\mathrm{E}^{\circ}$$ (V with respect to normal hydrogen electrode) values. Using this data obtain the correct explanations.

$$\begin{array}{ll} \mathrm{I}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{I}^{-} & \mathrm{E}^{\mathrm{o}}=0.54 \\ \mathrm{Cl}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cl}^{-} & \mathrm{E}^{\mathrm{o}}=1.36 \\ \mathrm{Mn}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+} & \mathrm{E}^{\mathrm{o}}=1.50 \\ \mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+} & \mathrm{E}^{\mathrm{o}}=0.77 \\ \mathrm{O}_{2}+4 \mathrm{H}^{+}+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O} & \mathrm{E}^{\mathrm{o}}=1.23 \end{array}$$

While $$\mathrm{Fe}^{3+}$$ is stable, $$\mathrm{Mn}^{3+}$$ is not stable in acid solution because

Redox reactions play a pivotal role in chemistry and biology. The values of standard redox potential $$\left(\mathrm{E}^{\circ}\right)$$ of two half-cell reactions decide which way the reaction is expected to proceed. A simple example is a Daniel cell in which zinc goes into solution and copper gets deposited. Given below are a set of half-cell reactions (acidic medium) along with their $$\mathrm{E}^{\circ}$$ (V with respect to normal hydrogen electrode) values. Using this data obtain the correct explanations.

$$\begin{array}{ll} \mathrm{I}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{I}^{-} & \mathrm{E}^{\mathrm{o}}=0.54 \\ \mathrm{Cl}_{2}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cl}^{-} & \mathrm{E}^{\mathrm{o}}=1.36 \\ \mathrm{Mn}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+} & \mathrm{E}^{\mathrm{o}}=1.50 \\ \mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+} & \mathrm{E}^{\mathrm{o}}=0.77 \\ \mathrm{O}_{2}+4 \mathrm{H}^{+}+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O} & \mathrm{E}^{\mathrm{o}}=1.23 \end{array}$$

Sodium fusion extract, obtained from aniline, on treatment with iron (II) sulphate and $$\mathrm{H}_{2} \mathrm{SO}_{4}$$ in presence of air gives a Prussian blue precipitate. The blue colour is due to the formation of

Chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules (approximately 6.023 $$\times$$ 10$$^{23}$$) are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear understanding of the mole concept. A 4.0 molar aqueous solution of NaCl is prepared and 500 mL of this solution is electrolysed. This leads to the evolution of chlorine gas at one of the electrodes (atomic mass : Na = 23, Hg = 200; 1 Faraday = 96500 coulombs)

The total number of moles of chlorine gas evolved is :