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For the spontaneous reaction 2C₂H₆(g) + 25O₂(g) → 16CO₂(g) + 18H₂O(g), what are the signs of ΔH, ΔS and ΔG in that order?

1. +, +, -
2. -, +, -
3. +, -, +
4. -, -, -

Correct answer: -, +, -

Solution

The reaction is exothermic, releasing heat, which gives it a negative ΔH. The increase in the number of gas molecules from reactants to products indicates an increase in entropy, resulting in a positive ΔS. Since the reaction is spontaneous at standard conditions, ΔG is negative.

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