# Enthalpy Calculator

Free Enthalpy Calculator provides the exact amount of enthalpy generated in a thermodynamic system. You have to provide the internal energy and volume of both reactants, products, and pressure of the system as input and press the calculate button to avail the enthalpy as output.

### How to Calculate Enthalpy?

Obtain the simple steps to the enthalpy of a thermodynamic system effortlessly. Follow these rules and get the answer.

- Check volume, the internal energy of reactants, products, the pressure of the system.
- Subtract products internal energy from the reactants internal energy.
- Subtract the volume of the products from the reactants.
- Multiply it with constant pressure.
- Add the result to the change in internal energy to get the enthalpy.

### Enthalpy Definition

Enthalpy is the amount of heat generated in a system. It is defined as the sum of the internal energy and the product of the pressure of the thermodynamic system. It is used to measure the energy of the system.

The real life examples of enthalpy change are hand warmers, refrigerators.

### Exothermic and Endothermic Reactions

The two types of thermodynamic reactions are endothermic reaction, exothermic reaction. Both these causes energy level differences. So, the difference is enthalpy.

**Endothermic Reaction: **It causes absorption of heat from the surroundings. Here, the change in enthalpy is positive as heat is gained.

**Exothermic Reaction: **It releases heat to the surroundings. Here, the change in enthalpy is negative as the heat is lost.

### Enthalpy Change Formula

The mathematical representation of enthalpy is** H = Q + pV**

Where,

- Q is the internal energy
- p is the pressure of the system
- V is the volume

The change in enthalpy takes two states i.e initial and final and pressure is constant during the reaction.

Enthalpy change equation is

**ΔH = ΔQ + p * ΔV**

**ΔH = (Q₂ - Q₁) + p * (V₂ - V₁)**

Where

- Q₂ is the internal energy of the products
- V₂ is the volume of the products
- Q₁ is the internal energy of the reactants
- V₁ is the initial volume of the reactants
- p is the constant pressure
- ΔH is the change in enthalpy
- ΔQ is the change in internal energy
- ΔV is the change in volume

The standard enthalpy formation for a chemical reaction is along the lines:

**ΔH°reaction = ∑ΔH°f(products) - ∑ΔH°f(reactants)**

Where,

- ΔH°reaction is the standard enthalpy change of formation
- ∑ΔH°f(reactants) is the sum of the standard enthalpies of formation of the reactants
- ∑ΔH°f(products) is the sum of the standard enthalpies of formation of the products

**Enthalpy Example:**

**Question: The change in internal energy of a system of 4.1 J, volume is 11 m3 and pressure of the system is 0.25 pa. Find the change in enthalpy of a system?**

Answer:

Given that,

Cange in internal energy ΔQ = 4.1 J

Change in volume ΔV = 11 m3

Pressure of the system p = 0.25 pa

Enthalpy change is ΔH = ΔQ + p * ΔV

ΔH = 4.1 + 0.25 * 11

= 4.1 + 2.75 = 6.85

Therefore, the enthalpy change is 6.85 J.

If you want to learn more chemistry topics calculators then have a glance at Chemistrycalc.Com and explore the concepts.

### FAQ’s on Change in Enthalpy Calculator

**1. How to calculate enthalpy?**

The detailed step by step process to calculate the enthalpy of a system is given here:

- Multiply the pressure of the system with the volume.
- Add product to the internal energy of the system to get the enthalpy.

**2. What is enthalpy in Physics?**

In physics, enthalpy is discussed as the change in heat. Adding internal energy to the product of pressure and volume exerted on a thermodynamic system forms the enthalpy.

**3. What is the enthalpy of endothermic and exothermic reactions?**

In an exothermic reaction, the overall energy of products is less than the reactants. So, the heat change is negative.

In the case of an endothermic reaction, enthalpy is positive as the products are higher in energy than the reactants.

**4. What is the change in the enthalpy equation?**

At a constant temperature and pressure, the enthalpy of a system equation is ΔH = ΔQ + p * ΔV.

**5. What is the unit of enthalpy?**

The SI unit of enthalpy is joule per kilometre or joule.