arrows a and d represent the enthalpy of the intermediate chemical reactions.\narrow c represents the…

arrows a and d represent the enthalpy of the intermediate chemical reactions.\narrow c represents the enthalpy of the overall chemical reaction.\narrow c indicates that the third intermediate reaction is exothermic.\narrow b indicates that the second intermediate reaction is exothermic.

arrows a and d represent the enthalpy of the intermediate chemical reactions.\narrow c represents the enthalpy of the overall chemical reaction.\narrow c indicates that the third intermediate reaction is exothermic.\narrow b indicates that the second intermediate reaction is exothermic.

Answer

Explanation:

Step1: Recall enthalpy concepts

Enthalpy change ($\Delta H$) is positive for endothermic reactions (heat - absorbed, arrow pointing up) and negative for exothermic reactions (heat - released, arrow pointing down). The overall enthalpy change of a reaction is the sum of the enthalpy changes of the intermediate reactions.

Step2: Analyze each option

  • Option 1: Arrows A and D represent the enthalpy of intermediate chemical reactions. This is correct as they are associated with individual steps in a multi - step reaction.
  • Option 2: Arrow C represents the enthalpy of an intermediate reaction, not the overall reaction. The overall reaction enthalpy is related to the sum of A, B, C and D in a proper way. So this is incorrect.
  • Option 3: Arrow C points downwards, which means $\Delta H_3<0$. A negative $\Delta H$ indicates an exothermic reaction. So this is correct.
  • Option 4: Arrow B points upwards, so $\Delta H_2 > 0$, which means the second intermediate reaction is endothermic, not exothermic. So this is incorrect.

Answer:

Arrows A and D represent the enthalpy of the intermediate chemical reactions.; Arrow C indicates that the third intermediate reaction is exothermic.