https://en.wikipedia.org/wiki/Enthalpy#Definintion
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here must What does "work required to achieve its pressure and volume:" mean?
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This is what I did make out of given answers <!-- being because in real  -->:
$$dQ=dU+PdV$$
for this work done by system is PdV<br>
now meaning considering total work to form is = internal energy + work done to occupy the space which is 
$$nadT=d(PV)$$
therefore this total is going to be really:
$$dH=dU+d(PV)$$
$$dH=dQ+dP**V$$
for opposite sign convention -dPV.