The enthalpies of all elements in their standard states are:(i) Unity (ii) Zero(iii) < 0 (iv) Different for every element
Question
The enthalpies of all elements in their standard states are:(i) Unity (ii) Zero(iii) < 0 (iv) Different for every element
Solution
The enthalpies of all elements in their standard states are zero. This is because by definition, the standard state of an element is its pure form at 1 atm and 25°C (or 298K). The enthalpy of formation for an element in its standard state is zero because there is no formation reaction needed when the element is already in its standard state. Therefore, the correct answer is (ii) Zero.
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