Delta H and q

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Delta H and q

Postby Jaira_Murphy_2D » Tue Feb 05, 2019 7:03 pm

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

JiangJC Dis2K
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Re: Delta H and q

Postby JiangJC Dis2K » Tue Feb 05, 2019 9:11 pm

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
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Re: Delta H and q

Postby Eunice Lee 1A » Sat Feb 09, 2019 10:02 am

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.

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Re: Delta H and q

Postby chloewinnett1L » Sat Feb 09, 2019 2:54 pm

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.

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