Question

define the term enthapy

Answer 1

enthalpy means energy

Answer 2

Enthalpy is defined as the sum of internal energy and pressure-volume energy.

i.e H = U + PV

While carrying out reactions, external agencies bring out changes in the reaction. For example, say a reaction is carried out in a laboratory. External agency like the pressure in the laboratory affects the reaction. Also the volume of the substance are not constant, it either increases or decreases.
So some work is done on that reaction. We cannot say that changes are brought about only because there is change in internal energy.  The energy also changes due to expansion or contraction at constant pressure and temperature.

So,in order to define those changes the term Enthaply was introduced.

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