The enthalpy of the species can be calculated using the sensible heat change (m*Cp*dT) but also needs a specific reference point. Most of the time 25C or 0C is chosen as a reference. Here since we start at 50C and want to know the heat change due to the reaction, we are using 50C as a reference and the point for the reaction enthalpy to be used.
I assume that the energy generation term due to heat of reaction was neglected for simplification purposes?
This screencast has been reviewed by faculty from other academic institutions.
Why was the final enthalpy for B expressed as the sum of the enthalpy at 50 degrees and the specific heat times a difference in temperature?
The enthalpy of the species can be calculated using the sensible heat change (m*Cp*dT) but also needs a specific reference point. Most of the time 25C or 0C is chosen as a reference. Here since we start at 50C and want to know the heat change due to the reaction, we are using 50C as a reference and the point for the reaction enthalpy to be used.