Electrochemistry

Define standard cell potential, $E^\ominus_{\text{cell}}$. Include a description of standard conditions.

Draw a labelled diagram of this electrochemical cell.

Include all necessary substances and relevant pieces of apparatus needed to measure the $E^\ominus_{\text{cell}}$.

It is not necessary to state the conditions used.

State the charge carriers that transfer current through the solutions and through the wire.

the solutions .............................. the wire ..............................

The standard electrode potential, $E^\ominus$, for the $\text{Zn}^{2+}(\text{aq})/\text{Zn}(\text{s})$ electrode is $-0.76 \text{ V}$.

Water is added to a standard $\text{Zn}^{2+}(\text{aq})/\text{Zn}(\text{s})$ electrode.

The new concentration of $\text{Zn}^{2+}(\text{aq})$ is $0.25 \text{ mol dm}^{-3}$.

Use the Nernst equation to calculate the electrode potential, $E$, for this new $\text{Zn}^{2+}(\text{aq})/\text{Zn}(\text{s})$ electrode.

Use this information to determine the change in oxidation state of manganese when this cell is discharging.

from .............................. to ..............................

Write the equation for the overall reaction that occurs when this cell is discharging.

The $E^\ominus$ for the $\text{ZnO}/\text{Zn}$ electrode is $-1.28 \text{ V}$.

Calculate the standard electrode potential, $E^\ominus$, for the $\text{MnO}_2/\text{Mn}_2\text{O}_3$ electrode.

Define standard cell potential, $E^\ominus_{\text{cell}}$.

An electrochemical cell is set up to measure $E^\ominus_{\text{cell}}$ of a cell consisting of an $\text{Fe}^{3+}/\text{Fe}^{2+}$ half-cell and a $\text{Cl}_2/\text{Cl}^-$ half-cell.

Draw a labelled diagram of this electrochemical cell.

Include all necessary substances. It is not necessary to state conditions used.

The cell reaction for the electrochemical cell in (b) is shown.

Calculate $\Delta G^\ominus$, in $\text{kJ mol}^{-1}$, for this cell reaction.

Use the Nernst equation to calculate the electrode potential, $E$, for the $\text{Fe}^{3+}/\text{Fe}^{2+}$ half-cell in this experiment.

[$E^\ominus$: $\text{Fe}^{3+}/\text{Fe}^{2+} = +0.77\text{ V}$]

Use your answer to (d)(i) to calculate $E_{\text{cell}}$ for this electrochemical cell.

Complete Table 5.1 to predict the substance liberated at each electrode during electrolysis of the indicated electrolyte with inert electrodes.

Table 5.1

State the relationship between the Faraday constant, $F$, and the Avogadro constant, $L$.

Use the experimental information in (b) and data from the table on page 23 to calculate a value for the Avogadro constant, $L$.

Show all working.

$\text{Avogadro constant, } L = \text{..............................}$

Describe the standard conditions used in the $\text{Sn}^{4+}/\text{Sn}^{2+}$ half-cell.

Complete the diagram below to show how $E^{\ominus}(\text{Sn}^{4+}/\text{Sn}^{2+})$ can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.

Equal volumes of $1.0\ \text{mol\ dm}^{-3}\ \text{Sn}^{2+}\text{(aq)}$ and $1.0\ \text{mol\ dm}^{-3}\ \text{Cl}^-\text{(aq)}$ are mixed.

Use relevant $E^{\ominus}$ values to explain whether a reaction occurs between these two ions.

Equal volumes of $1.0\ \text{mol\ dm}^{-3}$ of $\text{Sn}^{2+}\text{(aq)}$ and acidified $1.0\ \text{mol\ dm}^{-3}\ \text{VO}^{2+}\text{(aq)}$ are mixed.

Write an equation for the reaction that takes place in the resulting mixture.

A solution of $\text{SnCl}_2\text{(aq)}$ is electrolysed for a measured time using a steady current.

A mass of $2.95\ \text{g}$ of tin metal is produced at the cathode.

$\text{Al}_2\text{O}_3\text{(l)}$ is electrolysed for the same time by the same current.

Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.

Define standard electrode potential. Include details of the standard conditions used.

Complete the diagram below to show an electrochemical cell constructed from a $\text{Mg}^{2+}/\text{Mg}$ half-cell and a $\text{MnO}_4^-/\text{Mn}^{2+}$ half-cell. Label your diagram.

Use a positive (+) sign and a negative (–) sign to identify the polarity of each of the two electrodes in your diagram.
Use an arrow and the symbol ‘e’ to show the direction of electron flow in the external circuit.

Calculate the standard cell potential, $E^{\ominus}_{\text{cell}}$, of this cell.

$E^{\ominus}_{\text{cell}} = \text{.............................. } \text{V}$

Construct an equation for the cell reaction.

Predict how the cell reaction will change, if at all, when the solution in the $\text{Mg}^{2+}/\text{Mg}$ half-cell is diluted by the addition of a large volume of water. Explain your answer.

A molten magnesium salt is electrolysed for $15.0$ minutes by a constant current.

$4.75 \times 10^{22}$ magnesium atoms are produced at the cathode.

Calculate the value of the current used.

$\text{current} = \text{.............................. } \text{A}$

Describe the standard conditions used in the $\text{Sn}^{4+}/\text{Sn}^{2+}$ half-cell.

Complete the diagram below to show how $E^\ominus(\text{Sn}^{4+}/\text{Sn}^{2+})$ can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.

Equal volumes of $1.0\,\text{mol}\,\text{dm}^{-3}\ \text{Sn}^{2+}\text{(aq)}$ and $1.0\,\text{mol}\,\text{dm}^{-3}\ \text{Cl}^-\text{(aq)}$ are mixed.

Use relevant $E^\ominus$ values to explain whether a reaction occurs between these two ions.

Equal volumes of $1.0\,\text{mol}\,\text{dm}^{-3}$ of $\text{Sn}^{2+}\text{(aq)}$ and acidified $1.0\,\text{mol}\,\text{dm}^{-3}\ \text{VO}^{2+}\text{(aq)}$ are mixed.

Write an equation for the reaction that takes place in the resulting mixture.

A solution of $\text{SnCl}_2\text{(aq)}$ is electrolysed for a measured time using a steady current.

A mass of $2.95\,\text{g}$ of tin metal is produced at the cathode.

$\text{Al}_2\text{O}_3\text{(l)}$ is electrolysed for the same time by the same current.

Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.

Use these equations to deduce the half-equation for the reduction of carbon dioxide in this process.

Draw a fully labelled diagram of the apparatus that should be used to measure the standard electrode potential, $E^\ominus$, of $\text{O}_2(\text{g})$ in half-equation 1 under standard conditions. Include all necessary chemicals.

For the cell drawn in (a)(ii), use the Data Booklet to calculate the $E^\ominus_{\text{cell}}$ and deduce which electrode is positive.

Define the term standard cell potential.

An electrochemical cell is set up to measure the standard electrode potential of a cell, $E^\ominus_{\text{cell}}$, made of a Co$^{3+}$/Co$^{2+}$ half-cell and a Cl$_2$/Cl$^-$ half-cell.

Complete the table with the substance used to make the electrode in each of these half-cells.

Use data from the Data Booklet to calculate the $E^\ominus_{\text{cell}}$.

Write the equation for the overall cell reaction.

A fuel cell is an electrochemical cell that can be used to generate electrical energy.

A methanol-oxygen fuel cell can be used as an alternative to a hydrogen-oxygen fuel cell. When the cell operates, the carbon atoms in the methanol molecules are converted into carbon dioxide.

Calculate the volume of CO$_2$, in cm$^3$, formed when a current of 2.5 A is delivered by the cell for 30 minutes. Assume the cell is operated at room conditions.

Use these equations to deduce the half-equation for the reduction of carbon dioxide in this process.

Draw a fully labelled diagram of the apparatus that should be used to measure the standard electrode potential, $E^\ominus$, of $\text{O}_2(\text{g})$ in half-equation 1 under standard conditions. Include all necessary chemicals.

For the cell drawn in (a)(ii), use the Data Booklet to calculate the $E^\ominus_{\text{cell}}$ and deduce which electrode is positive.

Identify the substances liberated at the anode and at the cathode during the electrolysis of aqueous sodium sulfate, $\text{Na}_2\text{SO}_4\text{(aq)}$.

When molten sodium chloride is electrolysed, chlorine is liberated at the anode and sodium is liberated at the cathode.

A sample of molten sodium chloride is electrolysed for 1.50 hours using a current of 4.50 A.

Calculate the volume of chlorine and the mass of sodium that are liberated under room conditions.

Draw a diagram of the apparatus that would be used to measure the $E^\ominus$ value of this half-cell. Your diagram should be fully labelled to identify all apparatus, substances and conditions.

Use the Data Booklet to identify a substance that could be used to oxidise $\text{Mn}^{2+}$ ions to $\text{MnO}_4^-$ ions under standard conditions.

Write an equation for the reaction.