You are on your dream vacation at the beach when a major storm knocks out the power for days. Your cell phone is dead, and you want to make a battery to charge it. You find the following materials in the beach house: blue stone algaecide for pools, which can be used to make a 1.0 M Cu2+ solution; alum in the kitchen, which can be used to make a 1.0 M Al3+ solution; aluminum foil; copper wire; and bologna, which can be used as a salt bridge. (a) What are the half-reactions and overall reaction in the battery? (b) Draw a diagram using beakers, a voltmeter, and salt bridge to show how a battery can be constructed. Label the anode, cathode, and direction of electron flow.

Verified step by step guidance

1. Step 1: Identify the half-reactions for the redox process. For the copper half-reaction, Cu^{2+} + 2e^- \rightarrow Cu(s), and for the aluminum half-reaction, Al(s) \rightarrow Al^{3+} + 3e^-.
2. Step 2: Balance the electrons in the half-reactions. Multiply the copper half-reaction by 3 and the aluminum half-reaction by 2 to balance the electrons exchanged.
3. Step 3: Combine the balanced half-reactions to write the overall cell reaction. Ensure that the number of electrons lost in the oxidation half-reaction equals the number of electrons gained in the reduction half-reaction.
4. Step 4: Construct a diagram of the galvanic cell. Use two beakers, one containing the Cu^{2+} solution with a copper wire (cathode) and the other containing the Al^{3+} solution with aluminum foil (anode). Connect the electrodes with a voltmeter and use bologna as a salt bridge between the solutions.
5. Step 5: Label the anode and cathode in the diagram. Indicate the direction of electron flow from the anode (Al) to the cathode (Cu) through the external circuit, and the flow of ions through the salt bridge to maintain charge balance.

Key Concepts

Electrochemical Cells

Electrochemical cells are devices that convert chemical energy into electrical energy through redox reactions. They consist of two electrodes: the anode, where oxidation occurs, and the cathode, where reduction takes place. In this scenario, the battery is formed using copper and aluminum ions, which will undergo specific half-reactions to generate a flow of electrons, producing electricity.

Half-Reactions

Half-reactions represent the individual oxidation and reduction processes occurring in an electrochemical cell. Each half-reaction shows the transfer of electrons and the change in oxidation states of the reactants. For the battery in the question, the half-reactions will involve the oxidation of aluminum (losing electrons) and the reduction of copper ions (gaining electrons), which together contribute to the overall cell reaction.

Salt Bridge

A salt bridge is a crucial component in electrochemical cells that maintains electrical neutrality by allowing the flow of ions between the two half-cells. In this case, bologna can serve as a makeshift salt bridge, facilitating the movement of ions to balance the charge as electrons flow from the anode to the cathode. This ensures the continuous operation of the battery by preventing charge buildup that would otherwise halt the reaction.