Enthalpy Calculator

Enthalpy Calculator calculator can be used to calculate the enthalpy change of a reaction using Hess's law or bond energy method.

Input Parameters

Method: Hess's Law

Enter enthalpy change (kJ/mol) for the first reaction

Enter enthalpy change (kJ/mol) for the second reaction

Factor to multiply Reaction 1 by

Factor to multiply Reaction 2 by

Method: Bond Energy

Enter the average bond energy to be calculated

Calculation Results

Calculation Formula

Enthalpy Change (ΔH) = scaling1 × reaction1 + scaling2 × reaction2

Where:
ΔH: Total enthalpy change (kJ/mol)
scaling1: Scaling factor for Reaction 1
reaction1: Enthalpy change of Reaction 1 (kJ/mol)
scaling2: Scaling factor for Reaction 2
reaction2: Enthalpy change of Reaction 2 (kJ/mol)

Result

-- kJ/mol

Enter the input values and click Calculate to see the result

Enthalpy Calculator Calculator Usage Guide

Learn how to use the Enthalpy Calculator calculator and its working principles

How to Use Hess's Law Method

Hess's Law allows you to calculate the enthalpy change of a reaction by combining several known reactions. To use this method:

  1. Enter the enthalpy change (ΔH) for each known reaction in the appropriate fields.
  2. Adjust the scaling factors to match the desired reaction (the scaling factor represents how many times the reaction should be multiplied).
  3. Click the "Calculate" button to determine the total enthalpy change.

How to Use Bond Energy Method

The bond energy method calculates the average energy required to break a particular type of bond in a molecule. To use this method:

  1. Enter the bond energy value in the appropriate field.
  2. Click the "Calculate" button to see the result.

Working Principle

The Enthalpy Calculator works based on two main thermodynamic principles:

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same whether the reaction occurs in one step or multiple steps. This allows chemists to calculate enthalpy changes for reactions that cannot be measured directly by combining known reactions.

Bond Energy Method

The bond energy method calculates the total energy required to break all bonds in a molecule by summing the average bond energies of each type of bond. This method is particularly useful for estimating the enthalpy change of reactions involving bond breaking and formation.