Question

Consider the following processes:

1. 2A + (1/2)C, (H_1= 19 , kJ/mol)
2. (3/2B + 4C →2A + C + 3D), (H_2 = -3 , kJ/mol)
3. (E + 4A + C), (H_3= 10 , kJ/mol)

Calculate (H) for: (C + E + 3D).

A) 23 kJ/mol
B) 17 kJ/mol
C) 10 kJ/mol
D) 3 kJ/mol

Answer 1

The calculation of enthalpy change (ΔH) for the combination of processes requires additional information about each energy change and typically employs Hess's law due to the state function property of enthalpy.

Step-by-step explanation:

The student is asking about calculating the enthalpy change ΔH for the algebraic sum of several given processes in Chemistry. In this case, the formula for the enthalpy change is given by ΔH = (C + E + 3D), where C, E, and D are enthalpy changes associated with different steps of a reaction.

Given that the enthalpy changes for B, D, and E are 17 kJ/mol, 3 kJ/mol, and an unknown value, respectively, we can only solve this equation for C if the value for E were known. Typically, Hess's law is used for such calculations because enthalpy is a state function; the enthalpy change for a complete reaction is the sum of the enthalpy changes for individual steps, regardless of the process path.