Understanding Molar Enthalpy Change: Differences and Calculations Explained

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In summary, molar enthalpy change, also known as enthalpy of reaction, is the amount of heat energy that is either released or absorbed during a chemical reaction per mole of reactant. It is measured using a calorimeter and can be affected by factors such as temperature, pressure, concentration, and physical state of reactants. Molar enthalpy change can be either positive or negative, indicating an endothermic or exothermic reaction respectively. It is also related to bond energies, as breaking and forming bonds contribute to the overall enthalpy change of a reaction.
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What is the difference between enthalpy change in kj and molar enthalpy change?



Is molar relating to the concentration of solutions used or the moles of solutions used?



Do you work out the enthalpy change and divide by the amount of moles to get kj per mol?


CAN ANYONE HELP ME!
XXX
 
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Molar enthalpy change = (enthalpy change/no.of moles)
So, its units are kJ/mol
 
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I can provide some clarification on enthalpy change and molar enthalpy change. Enthalpy change, denoted as ΔH, is the measure of the change in heat energy during a chemical reaction or physical process. It is typically measured in units of kilojoules (kJ). On the other hand, molar enthalpy change, denoted as ΔHm, is the enthalpy change per mole of substance involved in the reaction. This means that the value of ΔHm is dependent on the number of moles of reactants and products involved in the reaction.

To answer your question, molar enthalpy change is related to the number of moles of substances used in the reaction, not the concentration of the solutions. To calculate molar enthalpy change, you would divide the enthalpy change (ΔH) by the number of moles of the substance involved in the reaction.

For example, if the enthalpy change for a reaction is 100 kJ and there are 2 moles of substance involved, the molar enthalpy change would be 50 kJ/mol.

I hope this helps clarify the difference between enthalpy change and molar enthalpy change. If you need further assistance, I recommend consulting a chemistry textbook or reaching out to a chemistry tutor for more in-depth explanations and calculations.
 

FAQ: Understanding Molar Enthalpy Change: Differences and Calculations Explained

What is molar enthalpy change?

Molar enthalpy change, also known as enthalpy of reaction, is the amount of heat energy that is either released or absorbed during a chemical reaction per mole of reactant.

How is molar enthalpy change measured?

Molar enthalpy change is measured using a calorimeter, which is a device that can accurately measure the change in temperature during a reaction. The change in temperature is then used to calculate the amount of heat energy released or absorbed.

What factors can affect molar enthalpy change?

The temperature, pressure, and concentration of reactants can all affect the molar enthalpy change of a reaction. Additionally, the physical state of the reactants (solid, liquid, or gas) can also impact the enthalpy change.

Is molar enthalpy change always positive?

No, molar enthalpy change can be either positive or negative. A positive enthalpy change indicates that the reaction is endothermic, meaning heat energy is absorbed. A negative enthalpy change indicates an exothermic reaction, where heat energy is released.

How is molar enthalpy change related to bond energies?

Molar enthalpy change is related to bond energies as chemical reactions involve breaking and forming bonds. Breaking bonds requires energy, while forming bonds releases energy. The difference in these energies determines the overall enthalpy change of the reaction.

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