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Which thermodynamic condition is favorable for converting a metal oxide into the metal?

1. ΔH is positive and TΔS is positive at low temperature
2. ΔH is positive and TΔS is negative at any temperature
3. ΔH is negative and TΔS is negative at high temperature
4. ΔH is negative and TΔS is positive at any temperature

Correct answer: ΔH is negative and TΔS is positive at any temperature

Solution

Conversion is favorable when dG = dH - TdS < 0. If dH is negative and TdS is positive, dG is negative at all temperatures, so this condition is favorable. (dH positive with TdS negative makes dG always positive - never favorable.)

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