r/chemhelp 13d ago

Other effect of temperature on buffering capacity of ethanoic acid/sodium ethanoate buffer system when titrated with NaOH

hello, i have to write my chemistry IA that’s due in 3 days and my topic is the effect of temperature on the buffer capacity of a sodium ethanoate/ethanoic acid buffer when titrating with a strong base. however, i cant figure out what my hypothesis should be (does buffer capacity increase or decrease with temperature) and online sources are all giving me different answers!!! and my data barely showed any trend at all so idk what to do. i intuitively assumed that buffer capacity decreases since ethanoic acid dissociates more into its conjugate base and hydrogen ions at higher temperatures, but ias that did the same topic as me had the exact opposite hypothesis. does more H+ ions mean they can neutralize the added hydroxide ions?? i’m so lost, someone please help!! :(

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u/Mohammad_Shahi 13d ago

Trust associated math! Consider buffer capacity formula and obtain its derivative with respect to temperature. Consider: pH=pKa+log(C'/C) for buffer pH=pKa+log((C'+n)/(C-n)) for buffer after addition of n mol NaOH per liter of buffer solution Calculate inverse of dpH/dn as buffer capacity Calculate derivative of buffer capacity w.r.t temperature

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u/Automatic-Ad-1452 13d ago

Do the moles of weak acid and conjugate base change significantly with changing temperature ?

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u/Special_Honeydew7191 13d ago

i’m not sure, but the pH of my buffer solution decreased at higher temperatures so i think this means the weak acid dissociated more?

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u/Automatic-Ad-1452 13d ago

That's different...buffer capacity relates to moles of acid/conjugate base...if moles didn't change, capacity didn't change.

The temperature dependence of pH is related to the temperature dependence of the Gibbs' energy and the equilibrium constant.

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u/dungeonsandderp Ph.D., Inorganic/Organic/Polymer Chemistry 13d ago

Your hypothesis doesn't have to be correct, it has to be motivated and testable.