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or does it depend on the reaction itself. I am conducting an experiment and the endothermic reactions have temperature changes of at least 8 degrees while the exothermic reactions have a change in 1 or 2 degrees. Is there a reason for that or is it just depending on the reaction?

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    $\begingroup$ It just depends on the reaction. $\endgroup$ – MaxW Mar 25 at 5:25
  • $\begingroup$ Just so we get this right, the endothermic reaction gets colder by 8 K (or Fahrenheit?), and the other(s) warmer by 1-2? What are those reactions? $\endgroup$ – Karl Mar 25 at 7:04
  • $\begingroup$ oh sorry, Im measuring it in Celsius. The endothermic decrease by up to 8 degrees celsius and the exothermic warmer by 1-2 celsius. They are five reactions: Sodium hydroxide solution + dilute hydrochloric acid. Sodium hydrogen carbonate solution + acetic acid. Copper (II) sulphate solution + magnesium ribbon. Dilute sulfuric acid + magnesium ribbon. Sodium hydrogen carbonate solution + citric acid. $\endgroup$ – Maryam Alshehhi Mar 25 at 7:30
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    $\begingroup$ Note to answer, just a comment on the way you might think, that seems wrong. There is no absolute change in temperature for a reactiin. Take and treat H of reaction and T of reaction as two different things. You cannot deduced H from a undefined T. Unless the T change you mentioned is that of a calorimeter. $\endgroup$ – Alchimista Mar 25 at 8:09
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    $\begingroup$ The absolute change in temperature depends on the absolute (not molar) reaction enthalpy and the heat capacity of the system (including the solvent and beaker!) in its final state and the amount of heat exchange with the environment in the timeframe of the experiment. $\endgroup$ – Karl Mar 25 at 18:36
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It depends on the reaction enthalpy.

Both reaction groups have a wide range of absolute reaction enthalpies to cause negligible or huge temperature difference, supposing the system is isolated.

The problem with some highly endothermic reactions is that they often require quite forced reaction conditions like high temperature, so it may be problematic to determine the temperature change directly, e.g. by calorimetry.

The temperature change can be then estimated from the reaction enthalpy of the reverse exothermic reaction and the molar heat capacities.

The reaction enthalpy can be often calculated from tabelated values for particular compounds.

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  • $\begingroup$ Can you re-phrase the last part of this answer? It's rather unclear, to the point where I'm not sure it's correct. $\endgroup$ – Karl Mar 25 at 7:01
  • $\begingroup$ @Karl I have tried to reformulate it. $\endgroup$ – Poutnik Mar 25 at 9:38

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