Consider the chemical equations shown here. which equation shows how to calculate hrxn for the equation below? what is hrxn for the overall reaction?

The enthalpy change of the reaction comes out to be -890 kJ

Explanation:

To calculate the enthalpy of the reaction divided in multiple steps, we use Hess's law. This law states that the heat absorbed or evolved in a given chemical equation remains same whether the process occurs in one step or several steps.

To apply this law, the enthalpy of the chemical equation is treated as ordinary algebraic expression and it can be added or subtracted to form the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes that occur during intermediate reactions.

For the given overall reaction:

The two intermediate reactions are as follows:

Reaction 1:  

Reaction 2:  

By adding both the reactions, we will get the overall enthalpy of the reaction, which is:

Hence, the enthalpy change of the reaction comes out to be -890 kJ