Question

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute $\mathrm{HCl}$ dilute ${\mathrm{HNO}}_3$, ${\mathrm{ZnCl}}_2$ and ${\mathrm{H}}_2\mathrm{O}$. In which of the above containers these solutions can be kept?

Answer 1

Step 1: Reactivity of copper in different solutions:

Dilute $\mathrm{HCl}$:

• Because copper does not interact with dilute ${\mathrm{H}}_2\mathrm{O}$, it could be handled in a copper jar.

Dilute ${\mathrm{HNO}}_3$:

• Dilute ${\mathrm{HNO}}_3$​ cannot be retained in a copper vessel due to the aforementioned chemical reaction:
• The reaction can be depicted as:
  $3\mathrm{Cu}\left(\mathrm{s}\right)+8{\mathrm{HNO}}_3\left(\mathrm{aq}\right)\to 3\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{NO}\left(\mathrm{g}\right)+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

${\mathrm{ZnCl}}_2$​:

• ${\mathrm{ZnCl}}_2$ can be maintained in a copper vessel since there is no interaction because copper is a less active metal than zinc and cannot displace from ${\mathrm{ZnCl}}_2$.

${\mathrm{H}}_2\mathrm{O}$:

• As there is no interaction between copper and water, water can be collected in a copper vessel.

Step 2: Reactivity of Aluminium with different solutions:

Dilute $\mathrm{HCl}$:

• Because aluminium interacts with dilute $\mathrm{HCl}$ to generate its salt, it cannot be preserved in an aluminium container.
• The chemical reaction can be depicted as:
  $2\mathrm{Al}\left(\mathrm{s}\right)+6\mathrm{HCl}\left(\mathrm{l}\right)\to 2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$

Dilute ${\mathrm{HNO}}_3$:

• Aluminium reacts with nitric acid to form a passive layer of aluminium oxide(${\mathrm{Al}}_2{\mathrm{O}}_3$​) which protects the aluminium from further oxidation. Therefore dilute nitric acid can be stored in an aluminium vessel.
• The chemical reaction can be depicted as:

$\mathrm{Al}\left(\mathrm{s}\right)+6{\mathrm{HNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3\left(\mathrm{aq}\right)+3{\mathrm{NO}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

${\mathrm{ZnCl}}_2$​:

• Aluminium being a more active metal than zinc displaces the latter from its solution, thus zinc chloride cannot be stored in the aluminium vessel.
• The chemical reaction can be depicted as:
  $2\mathrm{Al}\left(\mathrm{s}\right)+3{\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)\to 2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)+3\mathrm{Zn}\left(\mathrm{s}\right)$

${\mathrm{H}}_2\mathrm{O}$:

• Aluminium does not react with cold water and when attacked by steam also, it forms a protective aluminium oxide (${\mathrm{Al}}_2{\mathrm{O}}_3$ ) layer which prevents further reaction.
• The chemical reaction can be depicted as:
  $2\mathrm{Al}\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$

Step 3: The choice of vessel for solutions is given below:

• Dilute $\mathrm{HCl}$- Copper vessel
• Dilute ${\mathrm{HNO}}_3$- Aluminium vessel
• ${\mathrm{ZnCl}}_2$- Copper vessel
• ${\mathrm{H}}_2\mathrm{O}$ - Copper vessel