If you are looking for a way to write an equation that shows how the change in enthalpy of a reaction (δ𝐻𝐴) is related to the change in enthalpy of the reactants (δ𝐻𝐵) and the products (δ𝐻𝐶), then you have come to the right place. In this article, we will explain how to use diagram (i) to derive the equation and what it means in terms of thermodynamics.
What is diagram (i)?
Diagram (i) is a graphical representation of the energy changes that occur during a chemical reaction. It shows the energy levels of the reactants and the products, as well as the heat absorbed or released by the system. The diagram can be drawn as follows:
In this diagram, we can see that:
- The horizontal axis represents the progress of the reaction, from left (reactants) to right (products).
- The vertical axis represents the energy of the system, in terms of enthalpy (H).
- The blue line shows the energy level of the reactants, which is δ𝐻𝐵.
- The red line shows the energy level of the products, which is δ𝐻𝐶.
- The green line shows the energy level of the activated complex, which is the highest point on the curve and represents the transition state between the reactants and the products.
- The black arrow shows the direction of the reaction and indicates whether it is exothermic or endothermic. An exothermic reaction releases heat to the surroundings, while an endothermic reaction absorbs heat from the surroundings.
- The purple arrow shows the change in enthalpy of the reaction, which is δ𝐻𝐴. It is equal to the difference between the energy level of the products and the energy level of the reactants.
How to write an equation based on diagram (i)?
Based on diagram (i), we can write an equation that shows how δ𝐻𝐴 is related to δ𝐻𝐵 and δ𝐻𝐶 by using a simple formula: