Question

Which of the following metal does not liberate \(\mathrm{H_2}\) gas by reacting with HCl?

• A. Co
• B. Cu
• C. Ni
• D. Zn

Hint:

Only those metals which are above hydrogen in the reactivity series can liberate \(\mathrm{H_2}\) gas from dilute acids. Copper is below hydrogen, so it does not react with dilute HCl in this way.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Metals can only displace Hydrogen from an acid if they are more reactive than Hydrogen (i.e., they have a negative reduction potential).
Step 2: Formula Application:
Refer to the Electrochemical Series. Metals placed above Hydrogen ($E^{\circ} = 0$) liberate $H_2$. Metals below Hydrogen do not.
Step 3: Explanation:
Copper (Cu) has a positive reduction potential ($E^{\circ} = +0.34 \text{ V}$). This means it is less reactive than Hydrogen and cannot reduce $H^+$ ions to $H_2$ gas.
Step 4: Final Answer:
Copper (Cu) does not liberate $H_2$ gas.