InterviewSolution
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InterviewSolution
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Consider the equation NH4Br(s) → NH3(g) + HBr(g) carefully, and think about the sign of ∆S for the reaction it describes. ∆H = +188.3 kJ. Which response describes the thermodynamic spontaneity of the reaction? 1. The reaction is spontaneous only at relatively low temperatures. 2. All responses are 3. The reaction is spontaneous at all temperatures. 4. The reaction is not spontaneous at any temperatures. 5. The reaction is spontaneous only at relatively high temperatures |
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Answer» Correct option 2. All responses are Explanation: Entropy (S) is high for systems with high degrees of freedom, disorder or randomness and low for systems with low degrees of freedom, disorder or randomness. S(g) > S(l) > S(s). A reaction is spontaneous only when ∆G is negative. ∆H is positive for this reaction and ∆S is positive. ∆G = ∆H − T ∆S = (+) − T (+) = (+) − T ∆G will be negative (spontaneous reactions) only at high values of T. |
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