Chromyl chloride, $\text{CrO}_2\text{Cl}_2$, is made by warming a blend of potassium dichromate(VI) and potassium chloride with concentrated sulfuric acid.
$\text{K}_2\text{Cr}_2\text{O}_7 + 4\text{KCl} + 3\text{H}_2\text{SO}_4 \rightarrow 2\text{CrO}_2\text{Cl}_2 + 3\text{K}_2\text{SO}_4 + 3\text{H}_2\text{O}$
Apply the data below to complete the Hess’ Law cycle and work out the enthalpy change for the reaction, $\Delta H_r$.
(a)[2]
Use the enthalpy changes of formation provided to complete the Hess’ Law cycle and find $\Delta H_r$ for the reaction shown.
(b(i))[1]
Suggest the type of isomerism shown by the complex ions with formula $[\text{Cr}({\text{NH}}_3)_4\text{Cl}_2]^+$.
(b(ii))[4]
Explain why these two complex ions are coloured and have different colours.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “$\Delta H = [2(-580)+3(-286)+3(-1438)] - [-2061+4(-437)+3(-814)]$” …