Question

Metal X when treated with nitric acid yields $X{\left(N{O}_3\right)}_2$ and gas Y . Metal X is used for galvanisation and gas Y is characterised by reddish-brown fumes. Choose the correct statement regarding the given chemical reaction.​

• A. Metal acts as a reducing agent whereas nitric acid act as an oxidising agent.​
• B. Reaction that metal undergoes: $X^{+2}+2e^{-}\to X$
• C. Metal X is $Zn$, Salt is $Zn{\left(N{O}_3\right)}_2$ and gas is $C{O}_2$.​
• D. Reaction that nitric acid undergoes: $N^{+4}-e^{-}\to N^{+5}$

Answer 1

The correct option is A Metal acts as a reducing agent whereas nitric acid act as an oxidising agent.​

• We have given that Metal X is used for galvanisation and gas Y is characterised by reddish-brown fumes.
• We know that nitrogen dioxide gas has reddish-brown fumes and Zinc is used for galvnisation.
• So, the reaction of Zn with nitric acid is: $Zn\left(s\right)+4HN{O}_3\left(aq\right)\to Zn{\left(N{O}_3\right)}_2\left(aq\right)+2H_{2}O\left(l\right)+2N{O}_2\left(g\right)$
• Nitric acid is a strong oxidising agent, so it is oxidising Zn into $Zn{\left(N{O}_3\right)}_2$ and reducing itself. Therefore,
• Oxidation reaction: $Zn\left(s\right)\to Z{n}^{+2}\left(aq\right)+2e^{-}$
  So, the reducing agent is Zn.
• Reduction reaction: $N^{+5}\left(aq\right)+e^{-}\to N^{+4}\left(aq\right)$
  So, the oxidising agent is $HN{O}_3$
• In option A, Metal X is Zn, Salt is $Zn{\left(N{O}_3\right)}_2$ is correct but gas is $N{O}_2$ not $C{O}_2$.​
• In option B, Reaction that metal undergoes: $X^{+2}+2e^{-}\to X$​, this reaction is reduction but Zn undergoes oxidation.
• In option C, Reaction that nitric acid undergoes: $N^{+4}-e^{-}\to N^{+5}$​​, this is wrong reaction.
• In option D, Metal (Zn) acts as a reducing agent whereas nitric acid act as an oxidising agent.​ This is correct.