Heat of Reaction at Equilibrium Conversion Calculator

Heat of Reaction Formula:

\[ \Delta H_r = \frac{-\ln\left(\frac{K_2}{K_1}\right) \times R}{\frac{1}{T_2} - \frac{1}{T_1}} \]

Thermodynamic Constant at Initial Temperature (K₁):

Thermodynamic Constant at Final Temperature (K₂):

Initial Temperature (T₁):

Final Temperature (T₂):

Heat of Reaction per Mole (ΔHr):

J/mol

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Heat of Reaction at Equilibrium Conversion?

Definition: The heat of reaction (ΔHr) is the amount of heat energy absorbed or released during a chemical reaction at constant pressure.

Purpose: This calculator determines the enthalpy change of a reaction using equilibrium constants at different temperatures.

2. How Does the Calculator Work?

The calculator uses the van't Hoff equation:

\[ \Delta H_r = \frac{-\ln\left(\frac{K_2}{K_1}\right) \times R}{\frac{1}{T_2} - \frac{1}{T_1}} \]

Where:

\( \Delta H_r \) — Heat of reaction per mole (J/mol)
\( K_1 \) — Equilibrium constant at initial temperature T₁
\( K_2 \) — Equilibrium constant at final temperature T₂
\( T_1 \) — Initial temperature (K)
\( T_2 \) — Final temperature (K)
\( R \) — Universal gas constant (8.314 J/mol·K)

Explanation: The equation relates the change in equilibrium constants with temperature to the enthalpy change of the reaction.

3. Importance of Heat of Reaction Calculation

Details: Knowing ΔHr helps predict reaction spontaneity, design reactors, and understand energy requirements for chemical processes.

4. Using the Calculator

Tips: Enter equilibrium constants at two different temperatures (in Kelvin). The calculator will determine the enthalpy change.

5. Frequently Asked Questions (FAQ)

Q1: What does a negative ΔHr value mean?
A: A negative value indicates an exothermic reaction (heat is released), while positive means endothermic (heat is absorbed).

Q2: Why must temperatures be in Kelvin?
A: The Kelvin scale is absolute and ensures correct temperature differences in calculations.

Q3: How accurate is this method?
A: It assumes ΔHr is constant over the temperature range. For large ranges, more complex methods may be needed.

Q4: What if my equilibrium constants are very similar?
A: The calculation becomes sensitive to measurement errors. Use precise K values for accurate results.

Q5: Can I use this for any reaction?
A: Yes, as long as you have accurate equilibrium constants at two different temperatures.