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Or # Enthalpy Calculator

Enter the required parameters and the calculator will calculate the amount of enthalpy generated in the heating system, with the steps shown.

Calculate Enthalpy From:

Internal Energy & Volume:

Calculate From:

ΔH = ΔQ + p * ΔV
anA + bnB + cnC → dnD + enE + fnF

Internal Energy of Reactants

Internal Energy of Products

Volume of Reactants

Volume of Products

Change in Internal Energy

Change in Volume

Constant Pressure

an Coefficient

Reactant A

bn Coefficient

Reactant B

cnCoefficient

Reactant C

dn Coefficient

Product D

enCoefficient

Product E

fn Coefficient

Product F

Table of Content

 1 What is Enthalpy In Physics? 2 Unit of Enthalpy: 3 Enthalpy Change Equation: 4 How to Calculate Enthalpy Change? 5 Enthalpy of Exothermic and Endothermic Reaction: 6 Is enthalpy a negative change in heat or positive change in heat? 7 What is the main cause of enthalpy? 8 Can we calculate absolute enthalpy? 9 What is the relationship of enthalpy and pressure exerted on a system? 10 What are the dimensions of enthalpy?

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The enthalpy calculator is specially designed to calculate the exact amount of energy generated in an exothermic or endothermic reaction.

## What is Enthalpy in Physics?

“Enthalpy is the measure of the total energy released or absorbed in a  thermodynamic system”

Whenever a system changes its state from solid to liquid (the latent heat of fusion) or liquid to gas (the latent heat of vaporization), it requires a sufficient intake of energy to produce a comprehensive change in entropy.

### Unit of Enthalpy:

According to System International (SI), the entropy is expressed in joule per kilogram or simply joule.

## Enthalpy Change Equation:

At a constant temperature and pressure, the enthalpy equation for a system is given as follows:

#### ΔH = ΔQ + p * ΔV

where;

• ‘ΔH’ is the change in heat of a system
• ‘ΔQ’ is the change in the internal energy of a system
• ‘P’ is pressure on the system due to the surroundings
• ‘ΔV’ is the change in the volume of the system

#### anA + bnB + cnC → dnD + enE + fnF

the enthalpy equation is as follows;

“ΔH° of reaction = ∑ΔH°f(products) – ∑ΔH°f(reactants)”

where;

• an, bn, and cn are the coefficients of the reactants,
• A, B, and C are reactants,
• dn, and fn are coefficients of products formed,
• D, E, and F are products.
• ∑ΔH°f(products) is the change in heat during product formation,
• ∑ΔH°f(reactants) is the change in heat of reactants

However, the Heat Specific Calculator will allow us to determine the specific heat, mass of substance, and initial and final energy of any substance.

## Example of Enthalpy:

Using Hess’s Law evaluate the enthalpy of formation, ΔHfo, of FeCl3(s) from changes in enthalpy of the following two-step process that occurs under standard state conditions:

Fe(s)+Cl2(g)⟶ FeCl2(s)ΔH°= -258.69kJ
FeCl2(s)+3/2Cl2(g)⟶ FeCl3(s)ΔH°=−47.7kJ

Solution:

Need to focus on finding the enthalpy of the formation of FeCl3(s), which is equal to ΔH° for the reaction:
Fe(s)+5/2Cl2(g)⟶ FeCl3(s) ΔHfo=?
By looking at the reactions, see that the overall enthalpy ΔHfo for FeCl3(s) is equal to the sum of two reactions with known ΔH values.
Fe(s)+Cl2(g)⟶ FeCl2(s) ΔH°= -258.69kJ
FeCl2(s)+3/2Cl2(g)⟶ FeCl3(s) ΔH°= −47.7kJ

Fe(s)+5/2Cl2(g)⟶ FeCl3(s) ΔHfo= -306.39
The enthalpy of formation, ΔHf, of FeCl3(s) is −306.39 kJ/mol.

The enthalpy and the heat changes at each step in the reaction and overall heat, ΔHf° within a few seconds.

## The Enthalpy Table:

 Sr # . Name of Substance Symbolic Formula Standard Enthalpy of Formation ‘ΔH’ 1. Potassium Chloride KCl(s) -435.9 2. Potassium Chlorate KClO3(s) -391.4 3. Sodium Chloride NaCl(s) -411.0 4. Sodium Hydroxide NaOH(s) -426.7 5. Zinc Sulphide ZnS(s) -202.9 6. Zinc Oxide ZnO(s) -348.0 7. Copper Sulphate CuSO4(s) -769.9 8. Copper Oxide CuO(s) -155.2 9. Calcium Dioxide Ca(OH)2(s) -986.6 10. Water H2O(l) -285.8 11. Chloroform CHCl3(l) -131.8 12. Carbon Dioxide CO2(g) -393.5 13. Hydrogen Sulphide H2S(g) -20.1 14. Ammonia NH3(g) -46.2 15. Sulphur Trioxide So3(g) -395.2 16. Hydrochloric Acid HCl(g) -92.3 17. Nitrogen Oxide NO(g) +90.4 18. Nitrogen Dioxide NO2(g) +33.9 19. Phosphorus Pentachloride PCl5(g) -398.9 20. Phosphorus Trichloride PCl3(g) -306.4 21. Sulphur Dioxide SO2(g) -296.1

From the source of Wikipedia: Characteristic functions, Physical interpretation, Relationship to heat, Heat of reaction, Specific enthalpy, Throttling, Compressors.

From the source of Libre Text: Enthalpy Change Accompanying a Change in State, Effect of Temperature on Enthalpy, The Enthalpy of Phase Transition.