Chemistry - Metallurgy Question with Solution | TestHub

The correct variation of lines for Mg and Ca in an Ellingham diagram is shown in Option (D).

At 25°C, Ca has a more negative $\Delta G^{\circ }$ ($-1200kJ/mole$) than Mg ($-1150kJ/mole$), placing the Ca line below the Mg line.

The lines for both metals show a sudden increase in slope at their respective boiling points: approximately 1100°C for Mg and 1500°C for Ca. Because the Mg line rises more sharply after its earlier boiling point, it eventually crosses above the Ca line, which is consistent with the visual data in graph (D).