Question

How do you find the heat of formation of a solution?

Answer 1

Heat is the form of energy that is represented by the letter q and it is measured in units of joules, calories, etc. Heat is a transfer in three ways conduction, convection, and radiation. The heat of formation is also called the standard heat of formation or enthalpy of formation. When a substance is formed from its constituents in its natural states. When one mole of the substance is formed from its constituent’s atoms, ions, or elements that are in its natural states, the amount of heat released or absorbed is known as the heat of formation.

Formula used: The amount of heat released or absorbed is calculated using the formula as follows:
${{q = m \times C \times \delta T}}$

Complete step by step answer:
The amount of heat released or absorbed is calculated using the formula as follows:
${{q = m \times C \times \delta T}}$
Here, the heat evolved and absorbed is represented as q, the mass of the substance is presented as m, the specific substance is represented as ${\text{C}}$ , and the temperature difference is represented as ${{\delta T}}$.

Then calculate the moles of the substance as follows:
${\text{mole}}\left( {\text{n}} \right){\text{ = }}\dfrac{{{\text{weight}}}}{{{\text{Molecular}}\,{\text{weight}}}}$
Then divide the quantity of the heat absorbed or released by the number of the moles to the obtained quantity of the heat absorbed or released per mole.
${{\delta }}{{\text{H}}_{{\text{sol}}}} = \dfrac{{\text{q}}}{{\text{n}}}$
Here, n present the numbers of the moles of the substance. Here, heat is represented in units of the joules, and the unit of the moles is mol. Therefore, the unit of the heat of solution is joules per mol.

Note: The heat of formation of the solution is represented as ${{\delta }}{{\text{H}}_{{\text{sol}}}}$. It has either a positive or negative sign.
- If heat is released during the formation of the solution then the process is exothermic which leads to a decrease in the amount of energy and hence, carries a negative sign.
- If heat is absorbed during the formation of the solution then the process is endothermic which leads to an increase in the amount of energy and hence, carries a positive sign.