From Fig. 5.1, find the initial rate of reaction 1. Show your working.
The rate equation for reaction 1 is rate $= k[\text{S}_2\text{O}_8^{2-}][\text{I}^-]$. Suggest why a large excess of iodide ions makes it possible to determine the rate constant from the half-life in this investigation.
The reaction of persulfate ions, $\text{S}_2\text{O}_8^{2-}$, with iodide ions is catalysed by $\text{Fe}^{2+}$ ions. Write two equations to show how $\text{Fe}^{2+}$ catalyses reaction 1.
Describe the effect of an increase in temperature on the rate constant and the rate of reaction 1.
In aqueous solution, thiosulfate ions, $\text{S}_2\text{O}_3^{2-}$, react with hydrogen ions, as shown in reaction 2. reaction 2: $\text{S}_2\text{O}_3^{2-} + 2\text{H}^+ \rightarrow \text{SO}_2 + \text{S} + \text{H}_2\text{O}$ Under certain conditions, the reaction is first order with respect to $[\text{S}_2\text{O}_3^{2-}]$ and zero order with respect to $[\text{H}^+]$. The rate constant, $k$, for this reaction is $1.58 \times 10^{-2}\,\text{s}^{-1}$. Calculate the half-life, $t_{\frac{1}{2}}$, for reaction 2.
The compound nitrosyl bromide, NOBr, can be formed as shown in reaction 3. reaction 3: $2\text{NO}(g) + \text{Br}_2(g) \rightarrow 2\text{NOBr}(g)$ The rate is first order with respect to $[\text{NO}]$ and first order with respect to $[\text{Br}_2]$. The reaction mechanism consists of two steps. Suggest equations for the two steps in this mechanism. State which step is the rate-determining step.