Question

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Topic: Reaction Rates and Equilibrium
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Answer 1

When the enthalpy of the products is less than the enthalpy of the reactants, what is true of the reaction?

• It releases heat.
• It does work.
• It is not spontaneous.
• It absorbs heat.

Known: I have a basic understanding of this concept. I can understand the accompanying terms and concepts, but I can’t seem to connect them to enthalpy as a whole. At the moment I am looking for an alternative explanation.

Answer 2

For starters. What is enthalpy? When a process occurs at constant pressure, the heat evolved (either released or absorbed) is equal to the change in enthalpy.

Answer 3

@sweetburger I apologize for the intrusion, but I really like how you break chemistry concepts down. Would you be interested in revisiting the concept of enthalpy? Thank you~

Answer 4

Could the sign be negative? Because... the enthalpy of the products is lower than the enthalpy of the reactants of the system. So... the enthalpies of these reactions are less than zero, and are therefore an exothermic reactions.

Answer 5

@Yoongilife
You need to think of enthalpy differently to enthalpy change.

Enthalpy is basically a measure of how much 'chemical potential' energy (also thought of as 'latent energy') the reactants and the products possess. Now this cannot be measured directly. What you can measure is how the enthalpy changes when a reaction occurs.

This might help you. Focus on the energy profile curves.

http://www.docbrown.info/page03/3_51energyB.htm

Exothermic: reactants --> products + energy (energy released from reactants so products have less energy (enthalpy) than reactants)

Endothermic: reactants + energy --> products (energy absorbed into product, so higher enthalpy)

Answer 6

@mww, thank you very much. The website is super helpful. I have been searching high and low for a site that focuses and/or utilizes energy curves. I appreciate your detailed response. Thanks, again!