Question

The correct statement regarding the given Ellingham diagram is:

• A. At $800\, ^{\circ}C$, $Cu$ can be used for the extraction of $Zn$ from $ZnO$
• B. At $500\, ^{\circ}C$ coke can be used for the extraction of $Zn$ from $ZnO$
• C. Coke cannot be used for the extraction of $Cu$ from ${Ca_2O}$.
• D. At $1400\, ^{\circ}C$ $Al$ can be used for the extraction of $Zn$ from $ZnO$

Answer 1

The Correct Option is D

The given question involves interpreting an Ellingham diagram. An Ellingham diagram plots the change in Gibbs free energy (ΔG) of various reactions as a function of temperature. This diagram is instrumental in determining the feasibility of reduction reactions used in metal extraction.

For a reduction reaction to be feasible (i.e., spontaneous), the ΔG for the overall reaction must be negative. In the context of metallurgy, this means that the reducing agent (e.g., coke, aluminum) should result in a lower ΔG value for its oxidation than for the reduction of the metal oxide.

Let's analyze the options:

1. At $800 \, ^{\circ}C$, $Cu$ can be used for the extraction of $Zn$ from $ZnO$: While copper is used to reduce some metal oxides due to its lower position in the Ellingham diagram, it is not effective for ZnO. Copper's oxidation line generally lies above that of ZnO, indicating that it cannot reduce ZnO at this temperature.
2. At $500 \, ^{\circ}C$ coke can be used for the extraction of $Zn$ from $ZnO$: Coke, primarily composed of carbon, is a suitable reducing agent for many metal oxides at high temperatures due to its steep gradient on the Ellingham diagram. However, at $500 \, ^{\circ}C$, coke is generally not effective for reducing ZnO because the required conditions (high temperature) for feasible reduction aren’t met.
3. Coke cannot be used for the extraction of $Cu$ from ${Ca_2O}$: This option might have a typographical error as copper is typically extracted from copper oxides (like CuO), not from calcium oxides (CaO or Ca₂O). Assuming we're discussing common ores of copper, reducing copper from copper oxides with coke is feasible at high enough temperatures.
4. At $1400 \, ^{\circ}C$ $Al$ can be used for the extraction of $Zn$ from $ZnO$: Aluminum is a powerful reducing agent, utilized in aluminothermic reactions owing to its highly negative ΔG values at high temperatures. At $1400 \, ^{\circ}C$, aluminum can indeed effectively reduce ZnO, illustrating a classic thermite reaction.

Thus, the correct answer is: At $1400 \, ^{\circ}C$ $Al$ can be used for the extraction of $Zn$ from $ZnO$.

This option makes logical sense based on the position of aluminum relative to zinc oxide in an Ellingham diagram.