Classify each process as exothermic or endothermic.

Evaporation of alcohol from skin: liquid C3H8O+5.2 kJ 》 vaporized C3H8O. Burning of propane ina gas grill: C3H8+5O2 》 3CO2+4H2O+1652 kJ. Oxidation of iron to form rust: 4Fe+3O2》2Fe2O3+2221 kJ.

1. Endothermic reaction

2. Exothermic reaction

3. Exothermic reaction

Explanation:

1. Evaporation of alcohol from the skin, here the heat is absorbed by the alcohol so that it gets evaporated from the skin and it is an endothermic process. As the reaction says that, the energy is added to the system, so it is endothermic.

C₃H₈O + 5.2 kJ → C₃H₈O(g)

2. Burning of propane in a gas grill:

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O + 1652 kJ.

Here energy is released or given out which is termed as exothermic reaction.

3. Oxidation of iron to form rust:

4 Fe + 3O₂ → 2 Fe₂O₃ + 2221 kJ.

Here also energy is released along with the products, so it is termed as exothermic reaction.

Whenever energy is absorbed, the reaction is endothermic in contrast if the energy is released then the reaction is exothermic.

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