g/mol ↔ kJ/mol Calculator
Bidirectional converter for thermochemistry calculations. Convert between molar mass (g/mol) and energy values (kJ/mol) using energy-per-gram relationships.
Input Values
Select the unit that matches your energy value
Results
Calculation Breakdown
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Enter values and click "Convert" to see your results.
Conversion Formulas
g/mol → kJ/mol
kJ/mol = g/mol × kJ/g
Multiply molar mass by energy per gram
kJ/mol → g/mol
g/mol = kJ/mol ÷ kJ/g
Divide energy per mole by energy per gram
Sample Energy Conversions
| g/mol | kJ/g | kJ/mol | Action |
|---|---|---|---|
| 18 | 5 | 90 | |
| 44 | 3.5 | 154 | |
| 58.5 | 2 | 117 | |
| 180 | 1.2 | 216 |
Understanding Thermochemistry Units
What g/mol and kJ/mol Represent
g/mol measures molar mass - how many grams are in one mole of a substance. kJ/mol measures energy per mole - how much energy is released or absorbed when one mole of substance undergoes a reaction. These units connect mass and energy in thermochemistry.
Why Direct Conversion Isn't Always Possible
You can't directly convert g/mol to kJ/mol without additional information. Energy values depend on the specific reaction or property being measured. That's why this calculator requires an energy-per-gram value to bridge the conversion.
The Role of Energy per Gram
The kJ/g value acts as the conversion factor between mass and energy units. It represents how much energy is associated with each gram of substance, allowing you to scale from grams to moles.
Formula Explained in Simple Terms
For g/mol to kJ/mol: multiply the molar mass by the energy per gram. For kJ/mol to g/mol: divide the energy per mole by the energy per gram. The energy factor stays constant while you convert between the units.
Step-by-Step Example
A substance has molar mass 44 g/mol and releases 3.5 kJ per gram. To find kJ/mol: 44 × 3.5 = 154 kJ/mol. To reverse: 154 ÷ 3.5 = 44 g/mol. Same energy factor, just different directions.
Practical Energy Conversion Table
Different substances have different energy densities. Water (18 g/mol) might have combustion energy of 5 kJ/g, while organic compounds vary widely. The table shows how these factors combine for different molar energy values.
Common Misunderstandings
- Thinking molar mass and energy are directly related - they're not
- Forgetting that energy values depend on the reaction type
- Mixing up energy per gram vs energy per mole
- Not understanding that the same substance can have different energy values for different reactions
How This Calculator Helps
This bidirectional calculator eliminates confusion by clearly showing both conversion directions. Enter your known values and immediately see the relationship between mass-based and energy-based molar quantities.
Final Thoughts
Thermochemistry bridges mass and energy, but requires careful attention to units and conversion factors. Use this calculator to build intuition about how these fundamental quantities relate in chemical systems.