Spontaneity of Chemical reactions — Flashcards

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A spontaneous process occurs naturally without external help once started. Example: Rusting of iron — iron reacts with oxygen and moisture to form rust (Fe₂O₃) without any continuous external input.

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Hot water loses heat to the cooler surroundings until thermal equilibrium is reached. This happens naturally due to temperature difference, so it’s spontaneous. The reverse (water heating up by absorb…

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Entropy (S) is a thermodynamic property that measures the degree of randomness or disorder in a system. Higher disorder means higher entropy. For example, gases have more entropy than liquids, which h…

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H₂O(s) < H₂O(l) < H₂O(g). Solid water (ice) is most ordered (lowest entropy), liquid has moderate disorder, and gas has maximum randomness (highest entropy).

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The entropy change is given by: $$ \Delta S = \frac{q_{\text{rev}}}{T} $$ where $ q_{\text{rev}} $ is the heat transferred reversibly and $ T $ is the absolute temperature in Kelvin.

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Given: - $\Delta_{\text{fus}}H = 6.02\,\mathrm{kJ\,mol^{-1}} = 6020\,\mathrm{J\,mol^{-1}}$ - $T = 273\,\mathrm{K}$ $$ \Delta_{\text{fus}}S = \frac{\Delta_{\text{fus}}H}{T} = \frac{6020}{273} = 22.05\…

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Given: - $\Delta_{\text{vap}}H = 40.8\,\mathrm{kJ\,mol^{-1}} = 40800\,\mathrm{J\,mol^{-1}}$ - $T = 373\,\mathrm{K}$ $$ \Delta_{\text{vap}}S = \frac{\Delta_{\text{vap}}H}{T} = \frac{40800}{373} = 109.

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The second law states that for any spontaneous process, the total entropy of the universe increases: $$ \Delta S_{\text{univ}} = \Delta S_{\text{sys}} + \Delta S_{\text{surr}} > 0 $$ At equilibrium, $…