Write out the three rate equations that could match these data. rate =
Take one of the rate equations you wrote in (i), and calculate the rate constant, $k$. State the units of $k$ as well.
Explain why a value for the half-life, $t_{\frac{1}{2}}$, of this reaction cannot be calculated from the rate constant $k$ found in (ii) together with the equation $k = 0.693 / t_{\frac{1}{2}}$.
State two metals that function as heterogeneous catalysts in the removal of $\text{NO}_2$ from car engine exhaust gases.
Iron is a heterogeneous catalyst in the Haber process. Describe how this iron catalyst works.
$\text{Fe}^{2+}$ ions act as a homogeneous catalyst in the reaction between $\text{I}^- (aq)$ and $\text{S}_2\text{O}_8^{2-} (aq)$. Write equations for the two reactions that happen when $\text{Fe}^{2+} (aq)$ is added to a mixture of $\text{I}^- (aq) and $\text{S}_2\text{O}_8^{2-} (aq)$.
Explain the difference between a homogeneous catalyst and a heterogeneous catalyst.
Iron is a transition element. Explain why iron forms stable compounds in both the $+2$ and the $+3$ oxidation states.
The reduction half-equation for $\text{Fe}^{3+}$ under alkaline conditions, together with its $E^\circ$ value, is shown here: $\text{Fe(OH)}_3 + e^- \rightleftharpoons \text{Fe(OH)}_2 + \text{OH}^- \quad E^\circ = -0.56\,\text{V}$ Four further half-equations for reactions under alkaline conditions, together with their $E^\circ$ values, are shown here: $\text{Al(OH)}_4^- + 3e^- \rightleftharpoons \text{Al} + 4\text{OH}^- \quad E^\circ = -2.35\,\text{V}$ $\text{ClO}^- + \text{H}_2\text{O} + 2e^- \rightleftharpoons \text{Cl}^- + 2\text{OH}^- \quad E^\circ = +0.89\,\text{V}$ $\text{O}_2 + 2\text{H}_2\text{O} + 4e^- \rightleftharpoons 4\text{OH}^- \quad E^\circ = +0.40\,\text{V}$ $\text{Zn(OH)}_4^{2-} + 2e^- \rightleftharpoons \text{Zn} + 4\text{OH}^- \quad E^\circ = -1.22\,\text{V}$ Choose two oxidising agents that are able to oxidise $\text{Fe}^{2+}$ ions to $\text{Fe}^{3+}$ ions under alkaline conditions. For each of the two reactions that happen, write an equation and give the $E^\circ_{\text{cell}}$ value.