$3$ Iron is in the form of a at $27C$ and crystal at $1127C.$ The a$8$ kenistal structure change of iron occurs at $\frac{1}{b}ar$ of heat required to heat $280kg$ of iron from $27C$ to $1127C.,$ Fecas $=21+24\mathrm{.}103TJ,mo{l}^{\text{'}}K-1C{p}^{\text{'}-1},Fe()=24+8\mathrm{.}10TJ$ mol'R, AHreld $=900,7mo$ Mfe $=56gmo{l}^{-t}).$