Q14.162CP - Chemistry: Molecular Nature Of Matter And Change

Question

Bromine monofluoride (BF) disproportionates to bromine gas and bromine tri- and pentafluorides. Use the following to find Δ${{\mathbf{H}}^{\mathbf{o}}}_{\mathbf{rxn}}$for the decomposition of BrF to its elements:

$$\begin{gathered} \mathbf{3}{\mathbf{BrF}}_{\left(g\right)}\mathbf{\to }\mathbf{B}{{\mathbf{r}}_{\mathbf{2}}}_{\left(g\right)}\mathbf{+}{\mathbf{BrF}}_{{\mathbf{3}}_{\left(l\right)}}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{\Delta }{{\mathbf{H}}^{\mathbf{o}}}_{\mathbf{rxn}}\mathbf{=}\mathbf{-}\mathbf{125}\mathbf{.}\mathbf{3}\mathbf{KJ}\mathbf{\backslash }\mathbf{hfill} \\ \mathbf{5}{\mathbf{BrF}}_{\left(g\right)}\mathbf{\to }\mathbf{2}\mathbf{B}{{\mathbf{r}}_{\mathbf{2}}}_{\left(g\right)}\mathbf{+}{\mathbf{BrF}}_{{\mathbf{5}}_{\left(l\right)}}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{\Delta }{{\mathbf{H}}^{\mathbf{o}}}_{\mathbf{rxn}}\mathbf{=}\mathbf{-}\mathbf{166}\mathbf{.}\mathbf{1}\mathbf{KJ}\mathbf{\backslash }\mathbf{hfill} \\ {\mathbf{BrF}}_{{\mathbf{3}}_{\left(l\right)}}\mathbf{+}{\mathbf{F}}_{\mathbf{2}}\mathbf{\to }\left(g\right){\mathbf{BrF}}_{{\mathbf{5}}_{\left(l\right)}}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{\Delta }{{\mathbf{H}}^{\mathbf{o}}}_{\mathbf{rxn}}\mathbf{=}\mathbf{-}\mathbf{158}\mathbf{.}\mathbf{0}\mathbf{KJ}\mathbf{\backslash }\mathbf{hfill} \end{gathered}$$

Step-by-Step Solution

Answer

Enthalpy of reaction followed as:

$8{\mathrm{BrF}}_{\left(\mathrm{g}\right)}\to 2{\mathrm{BrF}}_{3_{\left(\mathrm{l}\right)}}+3{\mathrm{Br}}_{2_{\left(\mathrm{g}\right)}}+{\mathrm{F}}_{2_{\left(\mathrm{g}\right)}} \mathrm{\Delta }{{\mathrm{H}}^{\mathrm{o}}}_{\mathrm{rxn}}=-138.4\mathrm{KJ}$

Step 1: Enthalpy of reaction

It is defined as the heat of the action which is calculated to find out how much energy is required by the reaction to convert it’s one more into products that is equal to the change in energy of the system. a positive value indicates the reaction is endothermic that is heat is required and a negative value indicates the reaction is exothermic that heat is released.

Step 2: Enthalpy of the given reaction

To calculate the enthalpy of reaction when Bromine monofluoride (BF) disproportionates to bromine gas and bromine tri- and pentafluorides followed as:

 As given:

As enthalpy is equal to 

$\begin{array}{rcl}\mathrm{\Delta }{{\mathrm{H}}^{\mathrm{o}}}_{\mathrm{rxn}}& =& -125.3\mathrm{KJ}-166.1\mathrm{KJ}+158.0\mathrm{KJ}\\ & =& -138.4\mathrm{KJ}\\ & & \end{array}$