Enthalpy means

Explanation

H = E + PV.Enthalpy is a state function. Also known as heat content.It is measured in joules. It is not possible, to measure the enthalpy of a system in a given state. However, change in enthalpy ( ∆H ) can be measured for a change in the state of system . A change in enthalpy of a system can be written as:∆H = ∆E + ∆(PV) or ∆H = ∆E + V∆P + P∆V.Since, the gas is kept at constant pressure, = 0Hence ∆H = ∆E + P∆V .In case of liquids and solids, the changes in state do not cause signiicant volume change i.e. ∆V = 0. For such process, ∆H and ∆E are approximately the same i.e. ∆H ≈ ∆E.According to irst law of thermodynamics:∆E = q + w.If w is pressure - volume work done by the system, then:w = - P∆V So ∆E = q - P∆V.Putting the value of ∆E in equation (4) we get: ∆H = q - P∆V + P∆V.∆H = q.Since the pressure is constant, therefore,∆H = qp.