The enthalpy change for a reaction does not depend upon the. use of different reactants for the same product. difference in initial or final temperatures of involved substances.

Standard-State Enthalpy of Reaction (H)

Three factors can affect the enthalpy of reaction:

1.The concentrations of the reactants and the products
2.The temperature of the system
3.The partial pressures of the gases involved (if any)
4.The effects of changes in these factors can be shown relative to the standard-state enthalpy of reaction (H) which is the change in the enthalpy during a chemical reaction that begins and ends under standard-state conditions.

The factors affecting the enthalpy change of a reaction:

The enthalpy change of a reaction is a measure of the heat energy either released or absorbed during the reaction. It is influenced by several factors, but one of them does not affect it. Let's discuss each factor in detail:

Nature of reactants and products:
The enthalpy change of a reaction is highly dependent on the nature of the reactants and products involved. Different substances have different bond strengths, and breaking or forming these bonds requires varying amounts of energy. The enthalpy change is influenced by the type and number of bonds broken and formed during the reaction. For example, reactions involving strong covalent bonds tend to have larger enthalpy changes compared to reactions involving weak intermolecular forces.

State of reactants and products:
The physical state of the reactants and products also affects the enthalpy change of a reaction. Reactions involving changes in state, such as the melting of a solid or vaporization of a liquid, require additional energy to overcome intermolecular forces. This energy is either absorbed or released during the reaction, leading to a change in enthalpy. The enthalpy change is typically larger for reactions involving changes in state compared to reactions occurring within the same phase.

Enthalpy of reactants and products:
The enthalpy change of a reaction is directly related to the difference in enthalpy between the reactants and products. If the products have a lower enthalpy than the reactants, the reaction is exothermic, and heat is released to the surroundings. On the other hand, if the products have a higher enthalpy than the reactants, the reaction is endothermic, and heat is absorbed from the surroundings. The magnitude of the enthalpy change is determined by the specific values of enthalpy for the reactants and products.

Various intermediate reactions:
The enthalpy change of a reaction is NOT dependent on various intermediate reactions. Intermediate reactions refer to any chemical steps that occur between the reactants and the final products. These intermediate steps may involve the formation or breaking of chemical bonds, but they do not directly affect the overall enthalpy change of the reaction. The enthalpy change is determined by the net difference between the enthalpy of the reactants and products, regardless of the specific intermediate reactions that may occur. Therefore, the enthalpy change remains the same regardless of the presence or absence of intermediate steps.