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### Course: Class 12 Chemistry (India)>Unit 2

Lesson 1: Galvanic cells

# Electrodes and voltage of Galvanic cell

Identifying the anode and cathode in a galvanic cell, and calculating the voltage using standard electrode potentials.  Created by Sal Khan.

## Want to join the conversation?

• isnt the positive electrode called anode?
• Anode is where oxidation occurs. For a galvanic cell, it is negative and for an electrolytic cell it is the positive terminal.
• Why would the Voltage of the Zn2+ + 2e- be a negative number? Is that suggesting that the neutral Zinc always wants to lose 2 electrons?
• The voltages for the individual electrodes are given as voltages occurring with that particular metal as the cathode and a hydrogen electrode as the the anode. A positive value in this instance means that the hydrogen electrode gives up its electrons to the metal, and a negative value means that the metal gives up its electrons to the hydrogen. These values for voltage can be substituted in for any two electrodes that you use. Thus, the zinc will lose its electrons to any electrode with a reduction potential greater than -0.76, like copper in the video example.
• In my chemistry class we were taught to get the cell potential by using
"E°potential=E°cathode-E°anode," but Sal adds the voltages. I'm confused on how this works, can anyone explain?
• You're right 'E°cell=E°cathode-E°anode'. Cu is more electronegative than Zn, so Cu is the cathode and Zn is the anode. Therefore, in case of Cu and Zn, E°cell = E°cathode - E°anode = 0.34 - (- 0.76) = 0.34 + 0.76 = 1.10 V
• Anode is taken as positive and Cathode is taken as negative right, then why did sal wrote " - " for anode and vice versa ?
(1 vote)
• In a galvanic cell, the anode is negative. In an electrolytic cell, the anode is positive. Sal is correct here
• Isnt the anode positive and the cathode negative?
• The anode contains anions, which are negative, so the anode is negative and the cathode is positive. However, anodes oxidize, so they become less negative (more positive) during the reaction. Likewise, cathodes gain those electrons and become more negative (less positive). Because of this, the cathodes increase in mass while the anodes decrease in mass.
• What is the difference between his and Ecell= Ecathode- E anode? Is the positive one in the video cell potential, and and this is for energy of the cell? Could anyone clarify this please? Thanks!
• At , what is the difference between the two reactions?
• But I thought oxidation states and charges aren't the same thing?
(1 vote)
• The oxidation number of an ion is the same as its charge.