Question

When chlorine gas and hydrogen gas react to form hydrogen chloride, what will be the change of enthalpy of the reaction?

Answer 1

Explanation:

Reaction between chlorine and hydrogen gas will take place as follows.

           $Cl_{2}(g) + H_{2}(g) \rightarrow 2HCl(g)$

Since, standard enthalpy of $Cl_{2}(g)$ is 0 kJ/mol and $H_{2}(g)$ is also 0 kJ/mol. $\Delta H_{HCl}$ is -92.30 kJ/mol.

Hence, change in enthalpy will be calculated as follows.

                $\Delta H = \Delta H_{products} - \Delta H_{reactants}$

                                       = (-92.30 - 0) kJ/mol

                                       = -ve

Also, formation of bonds is taking place between both chlorine and hydrogen atoms. As a result, heat will be released during this process.

Thus, we can conclude that change in enthalpy will be negative.