Question

How do you calculate enthalpy change?

Answer 1

Hint As we know that change in enthalpy of a reaction is the amount of heat released or being absorbed as the reaction takes place. We can calculate the change in enthalpy in different ways depending on the specific situation.

Complete answer:
- We will discuss the simplest way of calculating the enthalpy change which uses the enthalpy of reactants and products. As we know that if we know these quantities then we can use the formula $\Delta H={{H}_{products}}-{{H}_{reactants}}$ to find the overall change.
- If we consider the reaction of sodium ion with chloride ion to form a sodium chloride compound, then we can calculate the enthalpy change in this way.
- As we know that chloride ion has an enthalpy of -167.4 KJ/mol and sodium ion has an enthalpy of -239.7 KJ/mol. And sodium chloride has an enthalpy of about -411 KJ/mol. Now, we will all these values given in the formula of enthalpy change as:
$\begin{align}
& \Delta H=-411KJ/mol-(-239.7KL/mol-167.4KJ/mol) \\
&\implies -411KJ/mol-(-407.1KJ/mol) \\
&\implies -411KJ/mol+407.1KJ/mol) \\
& \implies -3.9KJ/mol \\
\end{align}$
- So, we get the answer that there is almost 4KJ of energy per mole released during the formation of salt.
- Hence, in this way we can calculate the enthalpy change

Note:
- As we know that enthalpy is an energy-like property that has dimensions of energy. It is mainly measured in joules or ergs.
- It is found that there are several factors that affect the enthalpy of reaction, these are the temperature of the system, the concentration of the reactants and the partial pressure of the gases if any are involved.