longrightarrow $7\mathrm{.}28.$ A $25-g$ block of iron at $175C$ is dropped into a liter of water in an insulated flask at $20C$ and $1$atm. The specific enthalpy of iron is given by the expression hat$(H)(\frac{J}{g})=17\mathrm{.}3T(C).$

$($a$)$ What reference temperature was used as the basis for the enthalpy formula?

$($b$)$ Calculate the final temperature of the flask contents, assuming that the process is adiabatic, negligible evaporation of water occurs, negligible heat is transferred to the flask wall, and the specific enthalpy of liquid water at $1$ atm and a given temperature is that of the saturated liguid at the same temperature. $($Note: For this isobaric batch process, the energy balance reduces to $Q=H.$