Define standard enthalpy change of reaction.

Given the enthalpy changes $∆{\mathrm{H}}_1$ and $∆{\mathrm{H}}_2$ below, construct Hess's cycle that will enable you to find the enthalpy change,$∆{\mathrm{H}}_{\mathrm{f}}$, for the reaction:

$$\begin{gathered} {\mathrm{MgCO}}_3\left(\mathrm{s}\right)\to \mathrm{MgO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right); ∆{\mathrm{H}}_{\mathrm{r}}. \\ {\mathrm{MgCO}}_3\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{MgCl}}_2 \left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right); ∆{\mathrm{H}}_1. \\ \mathrm{MgO}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{MgCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right); ∆{\mathrm{H}}_2. \end{gathered}$$