Taking into account the definition of enthalpy of a chemical reaction, the quantity of heat released when 0.75 moles of Mg are burned is 451.5 kJ.
The enthalpy of a chemical reaction is known as the heat absorbed or released in a chemical reaction when it occurs at constant pressure. That is, the heat of reaction is the energy that is released or absorbed when chemicals are transformed into a chemical reaction.
The enthalpy is an extensive property, that is, it depends on the amount of matter present.
In this case, the balanced reaction is:
2 Mg(s) + O₂ (g) → 2 MgO(s) + 1204 kJ
This equation indicates that when 2 moles of Mg reacts with 1 mole of O₂, 1204 kJ of heat is released.
When 0.75 moles of Mg are burned, then you can apply the following rule of three: if 2 moles of Mg releases 1204 kJ of heat, 0.75 moles of Mg releases how much heat?
[tex]heat=\frac{0.75 moles of Mgx1204 kJ}{2 moles of Mg}[/tex]
heat= 451.5 kJ
Finally, the quantity of heat released when 0.75 moles of Mg are burned is 451.5 kJ.
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