The Enthalpy Change Per Mole Calculator helps determine the amount of heat absorbed or released during a chemical reaction, standardized to one mole of a substance. This is an important concept in thermochemistry and is use to compare reactions on a per-mole basis. The calculator is part of the Thermodynamics and Chemistry Energy Analysis Calculator category.
This tool is essential for students, researchers, and lab technicians who want to analyze energy changes accurately and compare results across different reactions and substances.
Formula of Enthalpy Change Per Mole Calculator
ΔH (kJ/mol) = q / n
Detailed Breakdown:
- ΔH = Enthalpy change per mole (in kilojoules per mole, kJ/mol)
- q = Heat released or absorbed during the process (in kilojoules, kJ)
- n = Number of moles of the substance involved (in mol)
How to Calculate Heat (q)
If heat is not directly given, calculate it using:
q = m × c × ΔT
Where:
- m = Mass of the substance or solution (in grams)
- c = Specific heat capacity (in J/g·°C; for water, typically 4.18 J/g·°C)
- ΔT = Temperature change = Final temperature − Initial temperature (in °C)
Convert to kilojoules:
q (kJ) = q (J) / 1000
How to Calculate Moles (n)
You can calculate moles using either:
- n = Mass / Molar Mass (for solids or pure substances)
- n = Concentration × Volume (for solutions; volume in liters)
Quick Reference Table
Here’s a useful table of values for common reactions and situations:
| q (kJ) | n (mol) | ΔH (kJ/mol) |
|---|---|---|
| 2.10 | 0.050 | 42.00 |
| 3.75 | 0.100 | 37.50 |
| 1.25 | 0.025 | 50.00 |
| 0.95 | 0.020 | 47.50 |
| 5.00 | 0.200 | 25.00 |
This table helps estimate enthalpy change quickly when typical values are involve.
Example of Enthalpy Change Per Mole Calculator
Suppose you perform a reaction where 2.508 kJ of heat is release, and you know 0.050 mol of product was form.
Step 1: Use the formula
ΔH = q / n = 2.508 / 0.050 = 50.16 kJ/mol
If the heat is released, the reaction is exothermic, and you may show this as:
ΔH = −50.16 kJ/mol
So, each mole of product formed releases 50.16 kJ of energy.
Most Common FAQs
It tells how much energy is absorbed or released per mole of a substance during a chemical reaction.
A negative value means the reaction is exothermic (releases heat). A positive value means it’s endothermic (absorbs heat).
Yes. It applies to any chemical process where heat change and mole quantity are known or measurable.