Reactants have a higher enthelpy

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In summary, during a reaction, the internal energy and enthalpy change. In an exothermic reaction, the reactants have a higher enthalpy and the products have a lower enthalpy, as shown by the energy profile diagram. However, the bond enthalpy for the reactants is lower and for the products is higher, as the reactant bonds require less energy to break but release more energy when new bonds are formed. This may be confusing as enthalpy and bond enthalpy are not the same thing. The energy during a reaction first increases to a maximum level (known as activation energy) and then decreases, as shown in a bell-shaped graph. The reaction does not occur in a linear manner and even
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GeneralOJB
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Am I right in saying that, in an exothermic reaction for example, the reactants have a higher enthalpy, and the products have a lower enthalpy, as seen from the energy profile diagram.
But the reactants have a lower bond enthalpy, and the products have a higher bond enthalpy, because a lower amount of energy is required to break the bonds in the reactants, but a higher amount of energy is released when the new bonds are formed. This just confused me as I thought enthalpy and bond enthalpy were the same thing!
 
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  • #2
During the course of reaction, the internal energy, and by extension, enthalpy, changes.

For e.g. During a reaction, the energy first increases to a certain maximum level (Difference in energy is called Activation Energy) then it comes down. (You know the bell-shaped graph)

The reactions doesn't takes place in arithmetic method. Even if burning is exothermic, it doesn't mean that we do not have to provide energy to do it.
 

What is enthalpy?

Enthalpy is the measure of energy in a thermodynamic system, often referred to as the "heat content" of a system.

What are reactants?

Reactants are the substances that are consumed in a chemical reaction to form new products. They are typically found on the left side of a chemical equation.

Why do reactants have a higher enthalpy?

Reactants typically have a higher enthalpy because they contain more potential energy than the products. This potential energy is released during a chemical reaction, resulting in a decrease in enthalpy.

How is enthalpy measured?

Enthalpy is typically measured in units of joules (J) or kilojoules (kJ) per mole (of substance). It can also be measured in calories (cal) or kilocalories (kcal).

What is the significance of reactants having a higher enthalpy?

The fact that reactants have a higher enthalpy is important because it helps us understand the direction of a chemical reaction. Reactants with higher enthalpy will release energy and form products with lower enthalpy, resulting in a spontaneous reaction.

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