## Delta H and q

$\Delta U=q+w$

Jaira_Murphy_2D
Posts: 31
Joined: Fri Apr 06, 2018 3:00 am

### Delta H and q

Can someone please explain the concept behind why Delta H is equal to q at constant pressure?

JiangJC Dis2K
Posts: 72
Joined: Fri Oct 12, 2018 12:16 am

### Re: Delta H and q

pressure and volume are inversely related. so at a constant volume, pressure is also constant. think about if you increase the pressure of a bike tire, the tire is also expanding and therefore there is a change in v, delta v. if delta v=0 then w=-pdeltav equals zero because the change in volume is zero. Therefore in the u=q+w equation, u equals q.

Eunice Lee 1A
Posts: 60
Joined: Wed Oct 03, 2018 12:16 am

### Re: Delta H and q

q represents the heat supplied to a system. Delta H represents the change in enthalpy, which is the change in energy as expansion work during heat transfer. When the pressure is constant, the heat supplied to a system is equal to the change in energy, so delta H and q are equal.

chloewinnett1L
Posts: 55
Joined: Fri Sep 28, 2018 12:20 am

### Re: Delta H and q

Also, enthalpy is specifically defined as the amount of heat absorbed or released under conditions of constant pressure. q represents heat absorbed/released, so qsubp is the same thing as enthalpy. qsubv is NOT the same thing as enthalpy.