Problem 161 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{HCl}\) cannot be stored in an aluminium vessel because (a) \(\mathrm{Al}\) is a highly reactive metal. (b) \(\mathrm{HCl}\) is an oxidizing acid (c) \(\mathrm{E}_{\mathrm{A}^{3+} / \mathrm{A}}^{0}\) is much smaller than \(E_{\mathrm{H}^{0}}^{0} / \mathrm{H}_{2}\) (d) All of these

Step-by-Step Solution

Answer

(d) All of these.

Step 1: Understand the Reactivity of Aluminium

Aluminium (\(\mathrm{Al}\)) is a highly reactive metal. This generally means that it can easily react with other substances such as acids, bases, or water. Thus, storing substances with reactive properties, like acids, in aluminium containers might lead to a reaction.

Step 2: Analyze \(\mathrm{HCl}\) Properties

\(\mathrm{HCl}\) (Hydrochloric acid) does not act as an oxidizing acid in typical scenarios. Oxidizing acids can accept electrons during a reaction which is not the main characteristic of \(\mathrm{HCl}\). So, this statement is misleading about \(\mathrm{HCl}\) when discussing storage.

Step 3: Evaluate Electrochemical Potential

We need to compare the standard electrode potential of aluminium, \(\mathrm{E}_{\mathrm{Al}^{3+} / \mathrm{Al}}^{0}\), with that of hydrogen \(\mathrm{E}_{\mathrm{H}^{+} / \mathrm{H}_2}^{0}\). Aluminium's standard electrode potential is \(-1.66 \text{ V}\), which is lower than hydrogen's \(0\text{ V}\). Hence, aluminium can be more easily oxidized by \(\mathrm{HCl}\), which can lead to a reaction breaking down the container.

Step 4: Summary and Conclusion

Based on the analysis in Steps 1 through 3, all options play a role in why \(\mathrm{HCl}\) should not be stored in an aluminium vessel. \(\mathrm{Al}\) can react due to its high reactivity and its potential to oxidize is present due to its lower electrode potential compared to hydrogen.

Key Concepts

Aluminium Storage

Aluminium storage must be approached with caution due to its high reactivity. Aluminium, being a lightweight metal, is often used for various applications. However, its reactive nature means it tends to engage in chemical reactions with other substances easily.
- When in contact with acids such as hydrochloric acid (HCl), aluminium can undergo a chemical reaction that can corrode the metal. This is not ideal for storage purposes, as it can lead to the deterioration of the vessel itself. - For safer storage options, non-reactive materials such as glass or certain plastics should be used when handling corrosive acids. This helps to ensure the integrity of the storage container and prevents potential hazards.

Standard Electrode Potential

The concept of standard electrode potential centers around an electrode's ability to gain or lose electrons, driving chemical reactions. Each element or compound has a unique standard electrode potential value, measured in volts (V).
- Aluminium's \(E_{\mathrm{Al}^{3+} / \mathrm{Al}}^{0}\) stands at \(-1.66\, \text{V}\). This indicates aluminium's propensity to lose electrons and be oxidized easily.- On the other hand, hydrogen's standard electrode potential \(E_{\mathrm{H}^{+} / \mathrm{H}_2}^{0}\) is \(0\, \text{V}\), serving as an elemental reference.- Since aluminium's potential is lower, it is more likely to oxidize than hydrogen in reactions involving acids like HCl.- The lower electrode potential of aluminium compared to hydrogen implies that HCl can oxidize aluminium, compromising its ability to safely hold the acid.

Hydrochloric Acid Properties

Hydrochloric acid (HCl) is a strong, corrosive acid with significant industrial and laboratory applications. Despite its strength, it is not regarded as an oxidizing acid.
- Unlike oxidizing acids such as nitric acid (HNO₃), HCl primarily acts to release hydrogen ions (H⁺) in solution. - Its primary function is to interact with bases to form salts and water in a neutralization reaction, or to react with metals to release hydrogen gas. - Because HCl can react aggressively with certain metals, it is crucial to choose appropriate storage materials that will not be affected by these reactions. A common practice is to use materials that are not susceptible to corrosion by the acid's properties. - For instance, neutral materials like plastic or glass are ideal for storage, as they do not react with HCl. This choice prevents potential hazards related to the storage and manipulation of such a corrosive agent.