Question

Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: PCl5(g) → PCl3(g) + Cl2(g)

Answer 1

Answer:

The value of $\Delta H$ for the desired reaction will be 249.75 KJ.

Explanation:

The desired reaction is shown below

$\textrm{PCl}_{5}\left ( g \right )\rightarrow \textrm{PCl}_{3}\left ( g \right )+\textrm{Cl}_{2}\left ( g \right )$

The desired reaction can be obtained by adding the given reactions and then dividing both sides by 4.

$P_{4}\left ( s \right )+6Cl_{2}\left ( g \right )\rightarrow 4PCl_{3}\left ( g \right ) \\4PCl_{5}\left ( g \right )\rightarrow P_{4}\left ( s \right )+10Cl_{2}\left ( g \right )$

Net Enthalpy change for the desired reaction

$\displaystyle \frac{3438-2439}{4} \textrm{ KJ} = 249.75 \textrm{ KJ}$

$\Delta H = 249.75 \textrm{ KJ}$