Hi! I'm new to the forums and currently reading about Chemical Thermodynamics. So here's what I know: ΔE = q - w So for constant volume reactions, no work is done hence: ΔE = q But for constant pressure reactions, heat be may released (for exothermic reactions) and work is done hence: ΔE = q - pΔV so ΔE ≠ q because some of the heat does work. So we define enthalpy H = E + PV, so, ΔH = ΔE + PΔV = q - pΔV + pΔV = q and hence for constant pressure reactions ΔH = q. My confusion is that the book says that the work term pΔV = (Δn)RT for these processes, but how can we hold the temperature constant since it is obviously changing as a result of the heat of the reaction? Any help would be greatly appreciated. Thanks!