Final answer:
The reaction 2C₂H₆ + 7O₂→4CO₂ + 6H₂O ΔH= -3119kJ is exothermic, as indicated by the negative enthalpy change (ΔH), meaning that heat is released during the reaction.
Step-by-step explanation:
The given chemical reaction: 2C₂H₆ + 7O₂→4CO₂ + 6H₂O ΔH= -3119kJ is an exothermic reaction. This is determined by the negative enthalpy change (ΔH), which indicates that heat is released to the surroundings during the reaction.
Exothermic reactions release energy, which is typically represented by a negative ΔH value in the enthalpy change of a reaction. When a reaction releases heat, it is losing energy to its surroundings, causing the temperature of the surroundings to rise. The energy released in this case is quantified as 3119 kJ, a substantial amount of energy.
For example, typical combustion reactions, where a substance burns in oxygen, are exothermic, like the burning of methane: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) + 213 kcal. This is opposite to endothermic reactions, which require energy to proceed and thus absorb heat from the surroundings, resulting in a positive ΔH, as shown in the decomposition of calcium carbonate: CaCO₃ (s) +177.8 kJ → CaO (s) + CO₂(g).