- #1
yifan
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Does anybody know why the entalpy change for a reaction differs in different pressure and temperature?
Enthalpy change is a measure of the amount of energy that is absorbed or released during a chemical or physical process. It is typically represented by the symbol ΔH and is measured in units of Joules (J).
According to the ideal gas law, pressure and volume are inversely related. When pressure increases, volume decreases and vice versa. This means that when pressure is increased, the particles in a system are forced closer together, resulting in stronger intermolecular forces and a decrease in enthalpy (ΔH). Therefore, an increase in pressure generally leads to a decrease in enthalpy.
Temperature and enthalpy are directly related. An increase in temperature leads to an increase in the kinetic energy of particles in a system, causing them to move faster and with more force. This results in weaker intermolecular forces and an increase in enthalpy (ΔH). On the other hand, a decrease in temperature leads to a decrease in enthalpy.
An endothermic reaction is a process in which energy is absorbed from the surroundings, resulting in a positive enthalpy change (ΔH). This means that the products have a greater enthalpy than the reactants. On the other hand, an exothermic reaction is a process in which energy is released to the surroundings, resulting in a negative enthalpy change (ΔH). This means that the reactants have a greater enthalpy than the products.
Enthalpy change is calculated by taking the difference between the enthalpy of the products and the enthalpy of the reactants. This can be represented by the equation ΔH = H(products) - H(reactants). The enthalpy values can be obtained from tables or by using calorimetry, which measures the heat flow of a reaction.