Question

How to calculate enthalpy

Answer 1

Enthalpy change can be calculated using the average energies of bonds broken and formed in a chemical reaction. The enthalpies of formation for reactants and products are also used to calculate enthalpy change. Hess's Law can be applied to calculate enthalpy changes of stepwise processes.

Step-by-step explanation:

The enthalpy change for a chemical reaction can be calculated using the average energies of the bonds broken in the reactants and the average energies of the bonds formed in the products. This can be expressed mathematically as

ΔΗ = ΣD(ED)

The enthalpies of formation for reactants are multiplied by the number of moles of each substance in the chemical equation, and then the total enthalpy of formation for the reactants is subtracted from the total enthalpy of formation for the products.

Hess's Law is also a useful tool for calculating enthalpy changes by using the enthalpy changes of stepwise processes.

Answer 2

Assuming this is a general question, the formula in which can be used to calculate enthalpy is:

H = Q + pV

Since enthalpy is the sum of the heat absorbed by the system and the work done when expanding, therefore in this formula we have:

H = enthalpy

Q = internal energy

p = pressure

V = volume