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.
