Question

Four hypothetical metallic elements $A,B,C$ and $D$ forms soluble nitrates having formulae $AN{O}_3,B(N{O}_3{)}_2,CN{O}_3$ and $D(N{O}_3{)}_3$.
Strips of each of the four metals were immersed in $0.1M$ aqueous solution of the other metal nitrates, and the following observations recorded.
1. Metal $B$ underwent reaction in all solutions.
2. Metal $A$ only reacted with $CN{O}_3$.
In order of increasing strength as reducing agents, the metals are :

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

Answer 1

Answer: (A)

$C,A,D$ and $B$

1. Metal $B$ underwent reaction in all solutions.
Hence, the metal $B$ can displace all the metals from their salt solutions. Hence, the metal $B$ has maximum strength as reducing agent.
2. Metal $A$ only reacted with $CN{O}_3$.
Thus metal $A$ can displace metal $C$ from its salt solution. Hence, the reducing strength of metal $A$ is greater than the reducing strength of metal $C$.
The increasing order of the strength as reducing agents is :
$C<A<D<B$