Q. 7.101 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the following as an oxidation or a reduction: ($7.6$)

a. ${\mathrm{Zn}}^{2+}(\mathrm{aq}.)+2{\mathrm{e}}^{-}\to \mathrm{Zn}\left(\mathrm{s}\right)$

b. $\mathrm{Al}\left(\mathrm{s}\right)\to {\mathrm{Al}}^{3+}\left(\mathrm{aq}\right)+3{\mathrm{e}}^{-}$-

c. $\mathrm{Pb}\left(\mathrm{s}\right)\to {\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}$

d. ${\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-}\to 2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$

Step-by-Step Solution

Answer

(a) The given reaction i.e. ${\mathrm{Zn}}^{2+}(\mathrm{aq}.)+2{\mathrm{e}}^{-}\to \mathrm{Zn}\left(\mathrm{s}\right)$ has undergone reduction

(b) The given reaction i.e. $\mathrm{Al}\left(\mathrm{s}\right)\to {\mathrm{Al}}^{3+}\left(\mathrm{aq}\right)+3{\mathrm{e}}^{-}$ has undergone oxidation

(c) The given reaction i.e. $\mathrm{Pb}\left(\mathrm{s}\right)\to {\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}$ has undergone oxidation

(d) The given reaction i.e. ${\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-}\to 2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$ has undergone reduction

Part (a) Step 1: Given information

We need to find that the reaction has undergone oxidation or reduction

Part (a) Step 2: Explanation

We know that

When there is gain of electrons then the reaction will undergo reduction.

And in the given reaction i.e. ${\mathrm{Zn}}^{2+}(\mathrm{aq}.)+2{\mathrm{e}}^{-}\to \mathrm{Zn}\left(\mathrm{s}\right)$ two electrons are gained by zinc

Therefore, The given reaction has undergone reduction 

Part (b) Step 1: Given information

We need to find that the reaction has undergone oxidation or reduction 

Part (b) Step 2: Explanation

We know that

When there is a loss of electrons then the reaction will undergo oxidation.

And in the given reaction i.e. $\mathrm{Al}\left(\mathrm{s}\right)\to {\mathrm{Al}}^{3+}\left(\mathrm{aq}\right)+3{\mathrm{e}}^{-}$ three electrons are lost by aluminum

Therefore, The given reaction has undergone oxidation 

Part (c) Step 1: Given information

We need to find that the reaction has undergone oxidation or reduction  

Part (c) Step 2: Explanation

We know that

When there is a loss of electrons then the reaction will undergo oxidation.

And in the given reaction i.e. $\mathrm{Pb}\left(\mathrm{s}\right)\to {\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}$  two electrons are lost by lead

Therefore, The given reaction has undergone oxidation 

Part (d) Step 1: Given information

We need to find that the reaction has undergone oxidation or reduction 

Part (d) Step 2: Explanation

We know that

When there is a gain of electrons then the reaction will undergo reduction.

And in the given reaction i.e. ${\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-}\to 2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$ two electrons are gained by chlorine

Therefore, The given reaction has undergone reduction