Delta H

[jlinwashington1B]

What does this refer to, and what’s the equation for it?

[Elle_Mendelson_2K]

Delta H is the change in enthalpy. H = U + PV is one of the equations.

[Jerome Mercado 2J]

Delta H is enthalpy of the system. When pressure is constant, Delta H can tell you if the system is absorbing or losing energy in the form of heat. A negative H is the loss of heat while a positive H is the absorption of heat.

The equation of the enthalpy of the system is the summation of H of the products subtracting the summation of H of the reactants.
To do this method you may need to know all the standard enthalpies of formation of each substance.

deltaH = delta H (products) - delta H (reactants)

Or

When change in enthalpy is reliant on work and internal energy:

deltaH = (q + w) + PdeltaV

[Aria Soeprono 2F]

It's also important to note that enthalpy is additive because of Hess's Law. It is a state function, so the change in enthalpy (Delta H) at each step of a multistep reaction can be added to get the total enthalpy change.

[Tarika Gujral 1K]

You can also use bond enthalpies to determine delta H:
Delta H = H bonds broken (reactants - H bonds formed (products)

But this is not always accurate, as it uses average enthalpy values for the bonds.

[Ashley P 4I]

Because it is a state function, it means that you can add/subtract two different delta H’s correct?

[Milena Aragon 2B]

Because it is a state function, it means that you can add/subtract two different delta H’s correct?

Yes, if you're asked to find the total enthalpy change you can add/subtract enthalpy values from multiple reactions

[Ashley P 4I]

Because it is a state function, it means that you can add/subtract two different delta H’s correct?

Yes, if you're asked to find the total enthalpy change you can add/subtract enthalpy values from multiple reactions

Thank you so much!