A chemical reaction has a enthalpy change of ΔH = -890.3 kJ/mol. Is this reaction exothermic or endothermic?

• A. Cannot be determined from ΔH
• B. Neither exothermic nor endothermic
• C. Endothermic
• D. Exothermic

Answer: (D)

Verified step by step guidance

1. Understand the meaning of enthalpy change (\$\Delta H\$): it represents the heat absorbed or released during a chemical reaction at constant pressure.
2. Recall the sign convention for \$\Delta H\$: if \$\Delta H < 0\$, the reaction releases heat to the surroundings; if \$\Delta H > 0\$, the reaction absorbs heat from the surroundings.
3. Given \$\Delta H = -890.3\ \text{kJ/mol}\$, note that the value is negative, indicating heat is released.
4. Since heat is released, classify the reaction as exothermic, which means energy flows out of the system.
5. Conclude that a negative enthalpy change corresponds to an exothermic reaction.