The enthalpy of the given reaction is

**Further Explanation:**

This problem is based upon Hess’s Law. Hess’s law is utilized for calculating the enthalpy change of a reaction that can be obtained simply by summation of two or more reactions. In accordance with the Hess’s law, of an overall reaction is obtained by adding the enthalpy change for each individual step reaction involved to obtain the overall reaction.

Enthalpy is defined as a state function and therefore its value depends upon the initial and final state of system but not upon the path. This is the reason that the overall reaction can be simply obtained by adding or subtracting the enthalpy change of the individual steps utilized to get the final reaction.

**Step 1:** The enthalpy change of the following reaction is .

…… (1)

The value of is -725 kJ.

**Step 2: **The enthalpy change of the following reaction is .

…… (2)

The value of is -74.5 kJ

**Step 3:** The enthalpy change of the following reaction is .

…… (3)

The value of is -1845 kJ.

**Step 4:** The enthalpy change of the following reaction is .

…… (4)

The value of is -476 kJ.

**Step 5:** The enthalpy change of the following reaction is .

…… (5)

**Step 6:** Multiply equation (2) by 6, equation (3) by 3 and equation (4) by 3. Add the resulting equation (3) and equation (1). Subtract the resulting equation (2) and equation (4). The final equation obtained is as follows:

…… (6)

**Step 7:** The expression to calculate is as follows:

…… (7)

Substitute -725 kJ for , -74.8 kJ for and -1845 kJ for and -476 kJ for in equation (7).

Hence, the enthalpy of is -4383.2 kJ.

**Learn more:**

**1.** Find the enthalpy of decomposition of 1 mole of MgO: brainly.com/question/2416245

**2.** Calculation of moles of HCl: brainly.com/question/5950133

**Answer details:**

**Grade:** Senior school

**Subject: **Chemistry

**Chapter: **Thermodynamics

**Keywords:** Hess’s Law, enthalpy, M, MCl3, Cl2, -4383.2 kJ, HCl, H2, -725 kJ, -74.8 kJ, -476 kJ, -1845 kJ, overall reaction.