Association Reply **Guide Questions 1-14
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I would like to ask everyone: the solubility heat given in the question is at 25°. Why can’t 25 degrees be chosen as the reference temperature? The version from Tianjin University also uses 0 degrees as the reference temperature; I’m very confused
Generally, the standard temperature is chosen as a reference. When encountering such questions, summarize them on your own; there’s no need to delve too deeply into them. The goal is to be able to solve similar questions in exams
Indeed, if 25 degrees is chosen for this problem, the calculated answer will be completely different. It’s also not specified at what temperature the heat of dissolution applies. I hope some experts can help answer this question @tiyiss
Refer to page 24 of the Tianjin University edition for the definition of integral heat of solution: the heat absorbed or released when 1 mole of solute dissolves in n moles of solvent at 25°C and 0.1013 MPa.
Thank you, but why are the calculation results different when using 0 degrees versus 25 degrees? I can’t figure out the reason
This post was last edited by zwp997 on 2015-7-23 09:50. Of course they are different; otherwise, wouldn’t temperatures in the range of 0–25°C be able to change freely without any need for heat transfer? ? To be honest, in theory any temperature can be chosen as the calculation basis, but it is necessary to specify the temperature basis so that the results are comparable, as different bases yield different results. Since the test questions often don’t provide a reference value, one can use a temperature value t as a reference, derive a general formula that includes t, and then substitute either 0 or 25°C into it; choose the option that yields a correct answer. This is effective for dealing with exam formats that consist of multiple-choice questions.
To pass the exam, this is definitely a good method for you. Logically, no matter which reference temperature is chosen, the calculated results should be the same. Could you explain in principle why the results differ when using 0 degrees and 25 degrees? Thank you. @tiyiss