How do you convert Joules to KJ/mol?
The correct answer and explanation is:
To convert Joules (J) to kilojoules per mole (kJ/mol), you need two conversion factors:
- Joules to Kilojoules: 1 kJ = 1,000 J. So, to convert from Joules to kilojoules, divide by 1,000.
- Per Mole Conversion: This step requires you to know how many moles are involved. The most common application of this conversion is when dealing with energy changes in chemical reactions, where the energy is provided for a given number of moles of a substance. In most cases, the energy value you are working with may already be per mole or may need to be divided by the number of moles to get the value per mole.
Example:
Suppose you have an energy value of 2,500 J and you want to convert it to kJ/mol for a reaction involving 2 moles of a substance:
Step 1: Convert Joules to Kilojoules
Since 1 kJ = 1,000 J, we can divide the energy in Joules by 1,000 to get kilojoules: 2,500 J÷1,000=2.5 kJ2,500 \, J \div 1,000 = 2.5 \, kJ
Step 2: Divide by the Number of Moles
To find the energy per mole, divide the energy in kJ by the number of moles: 2.5 kJ÷2 moles=1.25 kJ/mol2.5 \, kJ \div 2 \, \text{moles} = 1.25 \, kJ/mol
So, the energy is 1.25 kJ/mol.
Important Considerations:
- Ensure the energy value is given in Joules (J). If it’s in another unit (like calories), you must first convert that to Joules using the appropriate conversion factor (1 cal = 4.184 J).
- If the reaction involves more than one substance, you must adjust the moles based on the stoichiometric coefficients in the balanced chemical equation.
By applying these steps, you can convert any given energy value in Joules into kJ/mol, which is useful when analyzing chemical reactions, thermodynamic processes, or any other situation where energy per mole is relevant.