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What is enthalpy????

I am doing my GCSE coursework and my teacher has recommended to mention enthalpy in my background notes. As enthalpy isn't actually taught in the gcse I have no idea what it is. Please could someone explain simply what enthalpy actually is.

Thank you.
Reply 1
Avatar for lerjj
lerjj
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Original post by djm1999
I am doing my GCSE coursework and my teacher has recommended to mention enthalpy in my background notes. As enthalpy isn't actually taught in the gcse I have no idea what it is. Please could someone explain simply what enthalpy actually is.

Thank you.


It's simply a quantity of energy which is being exchanged with the environment. Reactions have an 'enthalpy change', which is the net heat loss or gain; molecules have 'bond enthalpy' (or some other terms, like 'enthalpy of formation) which is how much energy is given off/taken in when they are created from their elements.

Basically, enthalpy==energy. But chemists need multiple words for everything.
Reply 2
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FTSE420
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Original post by lerjj
It's simply a quantity of energy which is being exchanged with the environment. Reactions have an 'enthalpy change', which is the net heat loss or gain; molecules have 'bond enthalpy' (or some other terms, like 'enthalpy of formation) which is how much energy is given off/taken in when they are created from their elements.

Basically, enthalpy==energy. But chemists need multiple words for everything.


Would lattice enthalpy be the energy change in each individual atom?

Thanks for your reply :biggrin:
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FTSE420
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Reply 4
Avatar for lerjj
lerjj
13
Original post by djm1999
Would lattice enthalpy be the energy change in each individual atom?

Thanks for your reply :biggrin:


Lattice enthalpy refers to one of two things- lattice formation enthalpy, or lattice dissociation enthalpy. Numerically they are the same but with the opposite sign.

Lattice formation enthalpy is the energy exchanged with the environment when one mole of an ionic substance is made from gaseous ions. For example, the reaction Na+(g)+Cl-(g)-->NaCl(s) would represent the formation enthalpy for Sodium Chloride.

Dissociation enthalpy is how much energy you need to break apart an ionic lattice and remove every ion to infinity. This will usually be a positive value unless the compound is particularly unstable.

The greater the lattice enthalpy, the stronger the bonds are as it requires more energy to break up the lattice. The actual value quoted will be per mole of the lattice formed.

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