Chemistry - Metallurgy Question with Solution | TestHub

ChemistryMetallurgyEllingham diagram & Reduction methods, Refining of metalMedium2 minQB

ChemistryMediumsingle choice

Passage / Comprehension

Consider the following data:

At 25 °C:

$2 M g + O_{2} \to 2 M g O Δ G^{\circ} = - 1150 K J / m o l$

$2 C a + O_{2} \to 2 C a O Δ G^{\circ} = - 1200 K J / m o l$

At 1800 °C:

$2 M g + O_{2} \to 2 M g O Δ G^{\circ} = - 650 K J / m o l$

$2 C a + O_{2} \to 2 C a O Δ G^{\circ} = - 850 K J / m o l$

B.P. of Mg ≈1100 °C.

B.P. of Ca ≈ 1500 °C.

Temperature when CaO is possible to reduce by Mg :-

Answer:

Solution:

For reduction of CaO by Mg, reaction feasibility depends on ΔG° difference at same temperature.

At all given temperatures, CaO has more negative ΔG° than MgO, meaning CaO is more stable.

Therefore, Mg cannot reduce CaO at any temperature (thermodynamically impossible).

Even considering boiling points, Mg becomes gaseous above 1100°C but that does not change relative stability order.

Stream:JEESubject:ChemistryTopic:MetallurgySubtopic:Ellingham diagram & Reduction methods, Refining of metal

⏱ 2mℹ️ Source: QB

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