CHEMISTRY COMMUNITY

Can someone explain why qp=deltaH at constant pressure?

qp=delta H because the definition of enthalpy (H) is the amount of heat released/absorbed at a constant pressure. Therefore, q, being heat, equals delta H

This can also be proven with equations. Because ΔH = ΔU + PΔV and ΔU = q + w, you can plug ΔU into the ΔH equation as follows: ΔH = q + w + PΔV. Because w = -PΔV, the last two terms cancel each other out: ΔH = q - PΔV + PΔV, leaving us with ΔH = q at constant pressure. Hope this helps!

qp represents the amount of heat required to change the temperature of an object by a certain temperature for a certain number of moles (aka the amount of heat released or absorbed by the object). DeltaH is the amount of heat released or absorbed at a constant pressure.