Complete the three possible rate equations that fit these data. rate $=$ rate $=$ rate $=$
Select one of the rate equations you wrote in (i), and work out the value of the rate constant, $k$. State the units of $k$. $k = \ldots\ldots\ldots\ldots\ldots\ \text{units}$
Explain why a value for the half-life, $t_{1/2}$, of this reaction cannot be found using the value of the rate constant $k$ obtained in (ii) together with the equation $k = 0.693 / t_{1/2}$.
Identify two metals that serve as heterogeneous catalysts in the removal of $\text{NO}_2$ from car exhaust gases.
Iron is a heterogeneous catalyst in the Haber process. Describe the way this iron catalyst works.
$\text{Fe}^{2+}$ ions act as a homogeneous catalyst in the reaction between $\text{I}^-(\text{aq})$ and $\text{S}_2\text{O}_8^{2-}(\text{aq})$. Write equations for the two reactions that take place when $\text{Fe}^{2+}(\text{aq})$ is added to a mixture of $\text{I}^-(\text{aq})$ and $\text{S}_2\text{O}_8^{2-}(\text{aq})$.
Explain how a homogeneous catalyst differs from a heterogeneous catalyst.
Iron is a transition element. Explain why iron forms stable compounds in both the $+2$ and the $+3$ oxidation states.
The half-equation for the reduction of $\text{Fe}^{3+}$ in alkaline conditions, together with its $E^\circ$ value, is given below. $\text{Fe(OH)}_3 + e^- \rightleftharpoons \text{Fe(OH)}_2 + \text{OH}^-$\quad $E^\circ = -0.56\ \text{V}$ Four further half-equations for reactions in alkaline conditions, and 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, write an equation and give the value of $E^\circ_{\text{cell}}$.