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Ch.19 - Electrochemistry
Chapter 19, Problem 120b

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. (b) What voltage can be generated?

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insert step 1> Identify the half-reactions for the redox process. The copper (Cu) and aluminum (Al) will undergo redox reactions. The half-reactions are: Cu^{2+} + 2e^- \rightarrow Cu (reduction) and Al \rightarrow Al^{3+} + 3e^- (oxidation).
insert step 2> Determine the standard reduction potentials for each half-reaction. From a standard reduction potential table, find the values: E^\circ_{Cu^{2+}/Cu} and E^\circ_{Al^{3+}/Al}.
insert step 3> Calculate the standard cell potential (E^\circ_{cell}) using the formula: E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}. Here, the cathode is the copper half-reaction and the anode is the aluminum half-reaction.
insert step 4> Balance the number of electrons transferred in the half-reactions. Multiply the copper half-reaction by 3 and the aluminum half-reaction by 2 to balance the electrons.
insert step 5> Use the balanced half-reactions to confirm the overall cell reaction and ensure the stoichiometry is correct. The calculated E^\circ_{cell} will give the voltage that can be generated by the battery.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrochemical Cells

Electrochemical cells convert chemical energy into electrical energy through redox reactions. They consist of two electrodes: an anode where oxidation occurs and a cathode where reduction takes place. The flow of electrons from the anode to the cathode generates an electric current, which can be harnessed to power devices, such as a cell phone.
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Standard Electrode Potentials

Standard electrode potentials are measured voltages that indicate the tendency of a species to be reduced at an electrode. Each half-reaction has a specific potential, and the overall cell potential can be calculated by subtracting the anode potential from the cathode potential. This value helps predict the voltage output of the electrochemical cell.
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Salt Bridge Functionality

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. It prevents the buildup of charge that would otherwise stop the reaction. Commonly made from a gel or a solution of an inert electrolyte, it ensures the continuous flow of current by balancing the charges as the redox reactions proceed.
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Related Practice
Textbook Question
For the following half-reaction, E° = 1.103 V: Calculate the formation constant Kf for Cu(CN)2-.
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Textbook Question
Write a balanced equation for the overall cell reaction when a lead storage battery is being charged. Refer to Section 19.10.
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Open Question
Write a balanced equation for the overall cell reaction when a lead storage battery is being charged. Refer to Section 19.10.
Textbook Question

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. (d) An iPhone requires 5.0 V for charging. Can this battery charge the phone? Explain.

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Textbook Question

A storm has knocked out power to your beach house, and you would like to build a battery from household items to charge your iPhone. You have the following materials. alum in the kitchen, which can be used to make a 1.0 M Al3+ solution bleach, which is a solution that is approximately a 1.0 M in ClO-aluminum foil, a platinum necklace and bologna, which can be used as a salt bridge (a) What are the half-reactions and overall reaction in the battery?

202
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Textbook Question

A storm has knocked out power to your beach house, and you would like to build a battery from household items to charge your iPhone. You have the following materials. alum in the kitchen, which can be used to make a 1.0 M Al3+ solution bleach, which is a solution that is approximately a 1.0 M in ClO-aluminum foil, a platinum necklace and bologna, which can be used as a salt bridge (b) What voltage can be generated?

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