If the specific heat of iron is 0.449 J/g·K, what is the enthalpy change of this process for 100 g of Fe (s) ? Is the process endothermic or exothermic? Explain.

Full Question:

Although it is not really a chemical reaction, one could consider a cooling process to be analogous to the enthalpy change that occurs in a reaction. Consider the transformation

Fe (s, T = 300 K) → Fe (s, T = 250 K)

If the specific heat of iron is 0.449 J/g·K, what is the enthalpy change of this process for 100 g of Fe (s) ? Is the process endothermic or exothermic? Explain.

Answer:

ΔH = - 2245J

Explanation:

Specific heat capacity, Cp = 0.449 J/g·K

ΔH=MCpΔT

ΔT = 250K - 300K = - 50K

ΔH = 100 * 0.449 * (-50)

ΔH = - 2245J

The iron will lose (give off) heat energy to cool down. Hence, it is an exothermic process. The negative sign of the enthalpy confirms this.