Question

Name two metals which will displace hydrogen from dilute acids and two metals which will not.

Answer 1

Hint: This question is based on the reactivity of metals placed in the electrochemical series. We will write the electrochemical series; on the basis of that displacement of hydrogen can be determined.

Complete step by step answer:
Now, we know as mentioned it is based on the reactivity series of metals.
If we talk about the displacement of hydrogen from dilute acids, then we can say that metals placed above the hydrogen will displace hydrogen.
Now, some metals placed below the hydrogen will not displace the hydrogen; as they are less reactive than the hydrogen.
So, aluminium, and magnesium, or any other metal placed above hydrogen can be considered as an example of the metals that displace hydrogen from dilute acids; and mercury, and silver are the metals which will not displace hydrogen.
The reaction is shown below-
Reaction of Metal with Acid
\[\text{Metal + Acid}\to \text{Metal Salt+ Hydrogen}\]
     \[\begin{align}
  & Example \\
 & \begin{matrix}
   Magnesium \\
   Mg \\
\end{matrix}\begin{matrix}
   +HydrochloricAcid \\
   HCl \\
\end{matrix}\to \begin{matrix}
   MagnesiumChloride \\
   MgC{{l}_{2}} \\
\end{matrix}+\begin{matrix}
   Hydrogen \\
   {{H}_{2}} \\
\end{matrix} \\
\end{align}\]
     \[\begin{matrix}
   Alu\min ium \\
   Al \\
\end{matrix}\begin{matrix}
   +HydrochloricAcid \\
   HCl \\
\end{matrix}\to \begin{matrix}
   Alu\min iumChloride \\
   AlC{{l}_{3}} \\
\end{matrix}+\begin{matrix}
   Hydrogen \\
   {{H}_{2}} \\
\end{matrix}\]
     \[\begin{matrix}
   Mercury \\
   Hg \\
\end{matrix}\begin{matrix}
   +HydrochloricAcid \\
   HCl \\
\end{matrix}\to \text{No Reaction}\]
     \[\begin{matrix}
   Platinum \\
   Pt \\
\end{matrix}\begin{matrix}
   +HydrochloricAcid \\
   HCl \\
\end{matrix}\to \text{No Reaction}\]
In the last, we can conclude that aluminium, and magnesium will displace hydrogen from dilute acids; and mercury, and silver will not displace.

Additional Information:
We can define the reactivity series as it is the arrangement of metals in the descending order of the reactivity represented by them.
Let us write down the reactivity series.

Metals

Potassium

Lithium

Barium

Strontium

Calcium

Magnesium

Aluminium

Manganese

Zinc

Chromium

Iron

Cadmium

Cobalt

Nickel

Tin

Lead

Hydrogen

Antimony

Bismuth

Copper

Mercury

Silver

Gold

Platinum

Now, we can see the reactivity order of metal as mentioned above. The blue arrow indicates towards the metals that are highly reactive or least reactive.From the series, we can say that platinum is the least reactive, and potassium is the highly reactive metal.

Note:
It should be noted that these types of reactions occur with dilute acid like hydrochloric acid, nitric acids and sulfuric acids. Also, when it reacts with nitric acid, hydrogen gas is not evolved as nitric acid is a strong oxidizing agent and it will oxidize hydrogen to water.