Explanation of Enthalpy Change in Water Heating

Definition of Enthalpy
Enthalpy (H) is a thermodynamic property that represents the total heat content of a system. It is the sum of the internal energy (U) of the system plus the product of pressure (P) and volume (V) of the system.

Calculation of Enthalpy Change
The enthalpy change (∆H) of a system is the difference between the enthalpy of the products (Hf) and the enthalpy of the reactants (Hi). In the case of water heating, the enthalpy change can be calculated using the following formula:

∆H = Hf - Hi

Constant Pressure Process
In this case, the water is heated at constant pressure, which means that the pressure of the system remains constant during the heating process. Therefore, the change in enthalpy can be calculated using the formula:

∆H = mc∆T

Where m is the mass of the water, c is the specific heat capacity of water, and ∆T is the change in temperature of the water.

Calculation of Enthalpy Change in Water Heating
Given that the mass of water is 100 g, the specific heat capacity of water is 4.18 J/g°C, and the change in temperature is 50°C, the enthalpy change can be calculated as follows:

∆H = mc∆T
∆H = 100 g x 4.18 J/g°C x 50°C
∆H = 20,900 J

Therefore, the enthalpy change in heating 100 g of water from 50°C to 100°C at constant pressure is 20,900 J or 20.9 kJ.

Conclusion
In conclusion, the enthalpy change in water heating can be calculated using the formula ∆H = mc∆T, where m is the mass of the water, c is the specific heat capacity of water, and ∆T is the change in temperature of the water. In the case of constant pressure process, the enthalpy change can be calculated using the same formula. In this case, the enthalpy change in heating 100 g of water from 50°C to 100°C at constant pressure is 20.9 kJ.