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JEE Main levelSingle correct optionDifficulty 2 of 3mt071

The negative slope of the Ellingham line for $2 C + O X_{2} 2 CO$ arises because

A $Δ H^{\circ}$ becomes more negative as $T$ rises
Bthe number of gas moles increases, so $Δ S^{\circ}$ is positive
Cthe reaction is endothermic
Dthe number of gas moles decreases, so $Δ S^{\circ}$ is negative

Answer: B

The slope of the line equals

- Δ S^{\circ}

. Here one mole of

O X_{2}

gives two moles of

CO

, so entropy rises and

Δ S^{\circ} > 0

. Thus

Δ G^{\circ}

falls with temperature and the slope is negative.

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