Enthalpy Change of Formation of MgO: Explained

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Discussion Overview

The discussion revolves around the enthalpy change of formation of magnesium oxide (MgO) and the methodology used to determine this value, particularly focusing on the treatment of hydration effects when magnesium is added to aqueous hydrochloric acid (HCl).

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the enthalpy change due to hydration is disregarded in the calculation of MgO's enthalpy change of formation.
  • Another participant asks for further elaboration on the method used to determine the enthalpy change of formation of MgO.
  • A participant describes a method involving the calculation of the calorimeter's heat capacity using HCl and NaOH, followed by measuring the enthalpy changes for magnesium with HCl and for MgO with HCl, leading to the calculation of the enthalpy change of formation.
  • One participant asserts that the hydration effect is identical in both cases, implying it cancels out in the calculations.
  • Another participant expresses confusion regarding the assertion of identical hydration effects.
  • A participant reiterates that the hydration effect is the same in both cases, suggesting it does not affect the overall enthalpy change calculation.

Areas of Agreement / Disagreement

There is some disagreement regarding the treatment of hydration effects in the enthalpy change calculations, with one participant questioning the rationale while others assert that it cancels out. The discussion does not reach a consensus on this point.

Contextual Notes

The discussion does not clarify the specific assumptions made regarding hydration effects or the definitions used in the calculations, leaving some aspects unresolved.

semc
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Enthalpy change?

Hello, i was reading a book on thermodynamics and notice that when they are trying to find the enthalpy change of formation of MgO, they disregard the enthalpy change due to hydration when Mg is add to aqueous HCL. Why is this so?
 
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Could you elaborate further on the method that they used to determine the enthalpy change of formation of MgO?
 


well at first they calculate the heat capacity of the calriometer by adding HCL to NAOH. then they measure the enthalpy change of Mg with HCL. finally MgO with HCL. then they just use these values and calculate the enthalpy change of formation
 


Same hydration in both cases.

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dont really get it.What do you mean same hydration in both cases?
 


Hydration effect is identical in both cases, so it cancels out.

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