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For question 9.15, it asks you to calculate the entropy change for the freezing of 1.00 mol of H2O(l) at 0.00 degrees C. I get how to solve this by Delta S = Delta H/T but I understand that the only way Delta H = q is if there is constant pressure. This isn't explicitly mentioned in the problem so is this something we can assume for these type of questions that don't provide q?
Yes you can think of it like that at constant pressure. Well this makes sense because for phase changes (at constant temperature) the enthalpy of the reaction is basically delta H fusion, the amount of heat needed to convert 1 mol of solid to liquid. In this case delta H is negative since its the freezing of liquid at 0.0C.
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