To determine whether the reaction \( \text{H}_2 + \text{I}_2 \rightarrow 2\text{HI} \) is endothermic or exothermic, we need to consider the energy changes associated with the reaction.
- Endothermic Reactions: These absorb energy and have a positive enthalpy change (\( \Delta H > 0 \)).
- Exothermic Reactions: These release energy and have a negative enthalpy change (\( \Delta H < 0 \)).
In the context of your options:
- "9 KJ/mol endothermic" indicates that the reaction absorbs 9 kJ/mol of energy.
- "9 KJ/mol, exothermic" indicates that the reaction releases 9 kJ/mol of energy.
- "-9 KJ exothermic" indicates that the reaction releases 9 kJ of energy (a negative change).
- "-9 KJ endothermic" indicates that the reaction absorbs 9 kJ of energy (a negative change, which contradicts absorption).
Assuming the data provided indicates that the reaction requires energy (as suggested by the wording of "endothermic"), the correct interpretation here would likely be:
9 KJ/mol endothermic.
If "9 kJ" was meant to represent the energy associated with the reaction being absorbed, then the reaction is endothermic. If the value was negative, it would classify the reaction as exothermic.
If you have specific data about the enthalpy change of the reaction or more context, it would help clarify whether the reaction is endothermic or exothermic.