Hess’s Cycle Question 7

Some reactions, such as the formation of KClO₃ cannot be measured directly. Using the following equations, find the ΔH_fof KClO₃:

$KClO_3_{(s)}+3Mg_{(s)}\rightarrow KCl_{(s)}+3MgO_{(s)}\: \: \: \Delta H:-1852 kJ\: mol^-^1$

$K_{(s)}+\frac{1}{2}Cl_{2(s)}\rightarrow KCl_{(s)}\: \: \: \Delta H:-437 kJ\: mol^-^1$

$Mg_{(s)}+\frac{1}{2}O_{2(g)}\rightarrow MgO_{(s)}\: \: \: \Delta H:-602 kJ\: mol^-^1$

$clockwise = anticlockwise$

${\color{Magenta} x}{\color{Red} -1852} = {\color{Blue} -437 +3(-602)}$

$x=-391kJ$