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Questions and Answers
What is the oxidation number of sulfur (S) in the sulfate ion (SO4^2-)?
What is the oxidation number of sulfur (S) in the sulfate ion (SO4^2-)?
- +6 (correct)
- -2
- +2
- +4
Which of the following elements would have an oxidation number of zero?
Which of the following elements would have an oxidation number of zero?
- NaCl
- MgO
- H2O
- O3 (correct)
In a voltaic cell, which of the following describes the ion flow in the salt bridge?
In a voltaic cell, which of the following describes the ion flow in the salt bridge?
- Cations flow from the anode half-cell to the cathode half-cell to maintain charge balance. (correct)
- Cations flow from the cathode half-cell to the anode half-cell to maintain charge balance.
- Anions flow from the cathode half-cell to the anode half-cell to maintain charge balance.
- Ions are not able to flow through the salt bridge.
In a voltaic cell with a zinc anode and a silver cathode, what happens to the mass of each electrode over time?
In a voltaic cell with a zinc anode and a silver cathode, what happens to the mass of each electrode over time?
Which of the following statements accurately describes what occurs at the anode of a voltaic cell?
Which of the following statements accurately describes what occurs at the anode of a voltaic cell?
Which of the following is the correct half-reaction occurring at the cathode in a voltaic cell using copper (Cu) and silver (Ag)?
Which of the following is the correct half-reaction occurring at the cathode in a voltaic cell using copper (Cu) and silver (Ag)?
Why is a salt bridge necessary for the operation of a voltaic cell?
Why is a salt bridge necessary for the operation of a voltaic cell?
Given that silver (Ag) has a consistent +1 oxidation number in compounds, what is the oxidation number of carbon (C) in Ag2CO3?
Given that silver (Ag) has a consistent +1 oxidation number in compounds, what is the oxidation number of carbon (C) in Ag2CO3?
Which of the following is NOT a characteristic of the electrolytes used in voltaic cells?
Which of the following is NOT a characteristic of the electrolytes used in voltaic cells?
In a voltaic cell, if the zinc electrode is replaced with a copper electrode and the silver electrode is replaced with a gold electrode, how would the electron flow change?
In a voltaic cell, if the zinc electrode is replaced with a copper electrode and the silver electrode is replaced with a gold electrode, how would the electron flow change?
In potassium superoxide ($KO_2$), oxygen has an oxidation number of -2.
In potassium superoxide ($KO_2$), oxygen has an oxidation number of -2.
An alkaline earth metal, such as calcium, typically exhibits a +3 oxidation state in its compounds.
An alkaline earth metal, such as calcium, typically exhibits a +3 oxidation state in its compounds.
Elemental sulfur ($S_8$) has an oxidation number of +8 because it consists of eight sulfur atoms bonded together.
Elemental sulfur ($S_8$) has an oxidation number of +8 because it consists of eight sulfur atoms bonded together.
In the chlorate ion ($ClO_3^-$), chlorine has an oxidation number of +5.
In the chlorate ion ($ClO_3^-$), chlorine has an oxidation number of +5.
In a voltaic cell, the salt bridge prevents the flow of electricity between the two half-cells.
In a voltaic cell, the salt bridge prevents the flow of electricity between the two half-cells.
During the operation of a zinc-silver voltaic cell, the silver electrode loses mass as silver ions are reduced to silver metal.
During the operation of a zinc-silver voltaic cell, the silver electrode loses mass as silver ions are reduced to silver metal.
In a redox reaction, the species that loses electrons is said to be reduced.
In a redox reaction, the species that loses electrons is said to be reduced.
In an electrochemical cell, the cathode is the electrode where oxidation occurs.
In an electrochemical cell, the cathode is the electrode where oxidation occurs.
Electrons in a voltaic cell flow from the cathode to the anode through the external circuit.
Electrons in a voltaic cell flow from the cathode to the anode through the external circuit.
Spectator ions in the salt bridge react directly with the electrodes to facilitate electron transfer.
Spectator ions in the salt bridge react directly with the electrodes to facilitate electron transfer.
Flashcards
Oxidation Number
Oxidation Number
Another term for charge, indicating the number of electrons an atom has gained or lost.
Alkali Metal Oxidation
Alkali Metal Oxidation
Alkaline metals (Group 1) have a +1 oxidation number when in compounds.
Alkaline Earth Metals Oxidation
Alkaline Earth Metals Oxidation
Alkaline earth metals (Group 2) have a +2 oxidation number when in compounds.
Oxidation of Zinc
Oxidation of Zinc
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Oxidation of Silver
Oxidation of Silver
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Halogen Oxidation
Halogen Oxidation
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Oxidation of Oxygen
Oxidation of Oxygen
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Elemental Form Oxidation
Elemental Form Oxidation
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Voltaic Cells
Voltaic Cells
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Salt Bridge
Salt Bridge
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Anode
Anode
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Cathode
Cathode
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Oxidation
Oxidation
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Reduction
Reduction
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Redox Reaction
Redox Reaction
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Half Reaction
Half Reaction
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Phosphorus oxidation number in PO33-
Phosphorus oxidation number in PO33-
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Study Notes
- Electrochemistry involves oxidation numbers and voltaic cells
Oxidation Numbers
- Oxidation number is another term for charge.
- Oxidation numbers can be determined by looking at the periodic table and the element's family.
- Alkaline metals have a +1 oxidation number.
- Alkaline earth metals have a +2 oxidation number.
- Zinc (Zn) consistently has a +2 oxidation number.
- Silver (Ag) consistently has a +1 oxidation number.
- Halogens typically have a -1 oxidation number.
- Oxygen (O) typically has a -2 oxidation number, except in hydrogen peroxide (H2O2) or sodium peroxide, where it has a -1 charge.
Elemental Forms
- Elements in their elemental form have oxidation numbers of zero.
- Examples of elemental forms: P4, F2, Cl2, Ne, and Na.
Determining Oxidation Numbers
- To determine the oxidation number in a compound, consider the overall charge of the molecule.
- Example: In PO33- (phosphite ion), with an overall charge of -3, oxygen has a -2 charge, therefore, phosphorus has a +3 oxidation number.
- For PO33- (phosphite ion), the overall charge is -3.
- Oxygen has a -2 charge, so three oxygen atoms contribute -6.
- The equation: phosphorus charge + (-6) = -3, therefore phosphorus has a +3 charge.
Voltaic Cells
- Voltaic cells are found in car batteries and Duracell batteries.
- Voltaic cells consist of two half-cells, each with an electrode in an electrolyte solution.
- One cell contains a zinc electrode in a zinc solution (1 Molar).
- The other cell contains a silver electrode in a silver solution (1 Molar).
- A salt bridge connects the two half-cells, allowing ion flow to maintain charge balance.
- The salt bridge contains spectator ions (alkali metal and halogen).
- Salt bridges are made of spectator ions that don't react with the electrodes.
- The salt bridge conducts electricity, acts as an electrolyte, dissociates 100%, and does not react with zinc or silver.
- Wires connect the electrodes to a voltmeter to measure the potential difference.
- A wire connects the two cells and runs through a voltmeter.
Half-Reactions
- At the zinc electrode (anode): Zn(s) → Zn2+(aq) + 2e- (oxidation).
- At the silver electrode (cathode): Ag+(aq) + e- → Ag(s) (reduction).
- Zinc (Zn) solid becomes zinc ions (Zn+2) + 2 electrons (oxidation).
- Silver ions (Ag+1) gain two electrons to become silver solid (reduction).
- The zinc electrode loses mass as it transforms from solid to aqueous form.
- The silver electrode gains mass as silver ions are reduced to solid silver.
- The silver electrode gains mass, while the zinc electrode deteriorates from solid to aqueous.
- The reaction is called a redox, or reduction-oxidation, reaction.
Oxidation vs Reduction
- Oxidation is losing electrons, and reduction is gaining electrons (LEO GER).
- Oxidation is the losing of electrons (LEO).
- Reduction is the gaining of electrons (GER).
- The mnemonic "LEO lion goes GER" helps remember this.
Anode vs Cathode
- Anode is the site where oxidation occurs (an ox), and the cathode is the site where reduction occurs (red cat).
- The anode is the side where oxidation occurs (an ox).
- The cathode is the side where reduction occurs (red cat).
- Electrons flow from the anode to the cathode in alphabetical order.
- Electrons flow from the anode to the cathode.
- Mnemonic: an ox red cat.
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