Standard Enthalpy Calculator:
Enter the values of sum of the change in enthalpy of the products, dHp(J) and sum of the change in enthalpy of the reactants, dHr(J) to determine the value of Standard enthalpy, Es(J).
Standard Enthalpy Formula:
Standard enthalpy represents the heat change that occurs during a chemical reaction under standard conditions, typically 298.15 K (25°C) and 1 atm pressure.
It provides a reference point for comparing the enthalpy changes of different reactions. The standard enthalpy of a reaction is the difference between the standard enthalpy of the products and the reactants.
This concept is fundamental in thermochemistry, helping predict whether a reaction is exothermic (releases heat) or endothermic (absorbs heat).
Enthalpy of products – the total energy of the products formed in the reaction. Enthalpy of reactants – the total energy of the reactants before the reaction.
A chemical reaction occurs, with bonds breaking in reactants and new bonds forming in products. During this process, there might be an exchange of heat with the surroundings.
The standard enthalpy change considers the difference between the total enthalpies of the products and the reactants at standard conditions.
Standard enthalpy, Es(J) in joules is calculated by the difference of sum of the change in enthalpy of the products, dHp(J) in joules and sum of the change in enthalpy of the reactants, dHr(J) in joules.
Standard enthalpy, Es(J) = dHp(J) – dHr(J)
Es(J) = standard enthalpy in joules, J.
dHp(J) = sum of the change in enthalpy of the products in joules, J.
dHr(J) = sum of the change in enthalpy of the reactants in joules, J.
Standard Enthalpy Calculation:
- Finding Standard Enthalpy:
Given: dHp(J) = 50J, dHr(J) = 10J.
Standard enthalpy, Es(J) = dHp(J) – dHr(J)
Es(J) = 50 – 20
Es(J) = 30J.
- Finding change in enthalpy of the products:
Given: Es(J) = 40J, dHr(J) = 5J.
Standard enthalpy, Es(J) = dHp(J) – dHr(J)
dHp(J) = Es(J) + dHr(J)
dHp(J) = 40 + 5
dHp(J) = 45J.