Use the graph to work out the reaction rate at $40\,\text{s}$. Show every step in your working.
Use the graph to demonstrate that the overall reaction is first order. Give an explanation for your answer.
In another reaction that is also first order, $75\%$ of the reactant is consumed in $320\,\text{s}$. Determine the rate constant, $k$, for this reaction. State the units of $k$.
Define the term standard electrode potential, $E^\circ$.
In an electrochemical cell, a salt bridge is used. State its function. Explain your answer.
Complete the diagram of the apparatus that can be used to measure the $E^\circ$ of the $\text{Cr}_2\text{O}_7^{2-}(\text{aq}),\, \text{H}^+(\text{aq}) / \text{Cr}^{3+}(\text{aq})$ electrode against the standard hydrogen electrode. Your diagram must be fully labelled so that all apparatus, substances and conditions are identified.
The $E^\circ$ of the $\text{Cr}_2\text{O}_7^{2-}(\text{aq}),\, \text{H}^+(\text{aq}) / \text{Cr}^{3+}(\text{aq})$ electrode is $+1.33\,\text{V}$. Label the negative electrode and indicate the direction of electron flow in the external circuit when the current flows in your diagram in (c)(iii).
Ethanal is oxidised to ethanoic acid in the presence of $\text{Cr}_2\text{O}_7^{2-}$ ions. Write the ionic equation for the oxidation of ethanal to ethanoic acid using dichromate(VI) in acid conditions. Calculate the $E^\circ_{\text{cell}}$ for this reaction.
In an ethanol-oxygen fuel cell, $\text{CH}_3\text{CH}_2\text{OH}(\text{l})$ and $\text{O}_2(\text{g})$ are each in contact with inert electrodes dipped into an acidic solution. The cell reaction for the oxidation of ethanol by oxygen is shown. $2\text{CH}_3\text{CH}_2\text{OH} + \text{O}_2 \rightarrow 2\text{CH}_3\text{COOH} + 2\text{H}_2\text{O}$, $\quad E^\circ_{\text{cell}} = +2.01\,\text{V}$ Calculate $\Delta G^\circ$, in $\text{kJ mol}^{-1}$, for the oxidation of ethanol by oxygen.