Do you listen to podcasts? If your answer is yes, let’s talk! I listen to lots of different ones – history, stories, science, etc. We can share our favorites.
My favorite science podcast is ShortWave, a daily (about) 10 minute program on what’s going on in lots of different fields of science right now.
Go to: https://www.npr.org/podcasts/510351/short-wave (or listen however you get your podcasts) and browse the episodes. Choose one that sounds interesting and listen.
What was the name of the episode?
What was an interesting thing you learned?
Choose two more of the following science programs (no, I don’t listen to all of them) and choose one podcast from each. For each, answer the following questions. For many you have to go back to older episodes if you don’t want to listen to a coronavirus episode.
Feel free to listen to more than 2 more!
What program did you choose?
What was the name of the episode?
What was one interesting thing you learned?
What was your favorite program? Why?
ELECTROCHEMISTRY
https://www.youtube.com/watch?v=teTkvUtW4SA
Tyler Dewitt - Introduction to Electrochemistry
https://www.youtube.com/watch?v=7b34XYgADlM
Tyler Dewitt – Galvanic Cells (Voltaic Cells)
https://www.youtube.com/watch?v=2VT5rl8P84M
Professor Dave - Electrochemistry
New Al battery
http://www.iflscience.com/technology/new-aluminum-battery-charges-minute
Article you might find interesting.
Electrochemistry is the study of the interchange of electrical and chemical energy. This means you can use a chemical reaction to produce an electric current and you can use an electric current to produce a chemical change.
Oxidation –
Reduction –
Half Reaction –
Galvanic Cell – A device in which chemical energy is changed into electrical energy due to a spontaneous redox reaction. There are separate chambers for oxidation and reduction.
Oxidation
Reduction
Half Reaction
Called
Mass of Metal
+ or –
The red cat gets fat
An Ox and Red Cat
Electrons Flow:
Ions Flow:
Cell Potential (E) – This is the force “pulling” the electrons from the oxidizing half-cell to the reducing half-cell, measured in volts.
Standard Reduction Potential (E˚) – Measured compared to Hydrogen with 1M solutions.
For oxidation, reverse the reaction and change the sign. However, we do NOT multiply or divide the voltage if we multiply or divide the half-reaction.
The potential for the electrochemical cell is the sum of the potentials of the oxidation and the reduction reactions.
Ox Zn ® Zn 2+ + 2e- +.76v
Red Cu2+ + 2e- ® Cu +.34v
+1.10v
Electrons lost = Electrons gained
Spontaneous = + E
Ex. Cu and Fe
Ag and Fe
Zn and Fe
Voltaic Cell Simulation
https://chemdemos.uoregon.edu/demos/Electrochemical-Cells-Computer-Simulation-Voltaic-Cells-Zn-Cu-Ag
Faraday (F) – is the charge on one mole of electrons = 96500 coulombs/mol (C = coulomb = the quantity of electricity transferred by a current of 1 amp in 1 second).
The cell potential (E) is related to the free energy difference (∆G) for a chemical reaction. (Reminder: Volt = J/C and n =mol of e-)
∆G = -n FE
Ex. Is the reaction Cu2+ + Fe ® Cu + Fe2+ spontaneous (+E and -∆G)? ∆G?
The E depends on Solution Concentration!
If the change in concentration favors the forward reaction, E increases.
If the change in concentration favors the reverse reaction, E decreases.
This is NOT an equilibrium system! DO NOT USE LE CHATELIER!
https://www.youtube.com/watch?v=jousNNceCXs
Organic Chemistry Tutor – Nerst Equation Explained
The Nernst Equation is used to calculate E for a cell at nonstandard conditions.
E = E˚ - 0.0592 log Q
N
3 Mn2+ + 2 Al ® 3 Mn + 2 Al3+
Predict whether the E is larger or smaller than E˚ when:
(a) [Al3+] = 2.0 M and [Mn2+] = 1.0M
(b) [Al3+] = 1.0 M and [Mn2+] = 3.0M
(c) [Al3+] = 1.5 M and [Mn2+] = 0.5M
What to say…
An increase in cathode ion increases the driving force to produce voltage, a decrease in cathode ion decreases the drive to produce voltage
An increase in anode ion decreases the driving force to produce voltage, a decrease in anode ion increases the drive to produce voltage
A smaller reaction concentration produces a smaller driving force for the forward reaction, which produces a smaller cell potential.
A smaller reaction concentration increases the value of Q, which produces a smaller cell potential.
For any cell as the cell discharges, the concentrations change (reactants decrease and products increase). The cell discharges until the reaction reaches equilibrium E = 0 and ∆G = 0. At this point the battery is dead.
Electrolysis
https://www.youtube.com/watch?v=dRtSjJCKkIo
Tyler DeWitt - Electrolysis
An electrolytic cell uses an electric current to make a nonspontaneous redox reaction to occur. The amount of chemical change that occurs depends on the amount of current and how long that current (amps) flows.
Electrolytic Cell simulation
http://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/html5/Electro/Electro.php
Electrolysis http://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/html5/Electro/Electro.php
Reminder: 1 amp = 1C/sec
This calculation is all unit conversions.
Ex. What mass of copper is plated out when a current of 10.0 amps passes through a solution containing Cu2+ for 30 minutes?
Ex. How long must a current of 5.00 A be applied to a solution of Ag+ to produce 10.5 g of Ag metal?
PRACTICE:
1.Consider ONLY the following half-reactions for Question 1:
HALF-REACTION Eo (V)
Al3+ (aq) +3e- ® Al (s) -1.66
Ni2+ (aq) + 2e- ® Ni (s) -0.25
Sn2+ (aq) + 2e- ® Sn (s) -0.14
Hg22+ (aq) + 2e- ® 2 Hg (l) +0.79
Ag+ (aq) + e- ® Ag (s) +0.80
Ce4+ (aq) + e- ® Ce3+ (aq) +1.61
__________a) Which species (specific ion or atom) is the weakest oxidizing agent in the list?
__________b) Which species is the strongest oxidizing agent?
__________c) Which species is the strongest reducing agent?
__________d) Which species is the weakest reducing agent?
__________e) Will Sn(s) reduce Ag+(aq) to Ag(s)? (yes or no)
__________f) Will Hg(l) reduce Sn2+(aq) to Sn(s)? (yes or no)
___________________g) Name all of the ions (on this list) that can be reduced by Sn(s).
___________________h) Name all of the metals (on this list) that can be oxidized by Ag+(aq)?
i)What reaction leads to the maximum positive standard potential? Indicate the Eonet. Write the balanced net ionic equation.
j) If the Ni2+(aq)/Ni(s) half cell is combined with the Hg22+(aq)/Hg(l) half cell, write an equation for the spontaneous reaction that occurs. What will be its standard potential?
k) Write the spontaneous reaction that occurs when the half-reactions Ag+(aq)/Ag(s) and Ni2+(aq)/Ni(s) are combined. What is the value of Eonet for this reaction?
2. In an electrolysis cell, a current of 0.250 ampere is passed through a solution of a chloride of iron, producing Fe(s) and Cl2(g). (The formula for the chloride of iron is meant to be ambiguous. See (b) below)
a)Write the equation for the half-reaction that occurs at the anode.
b)When the cell operates for 2.00 hours, 0.521 gram of iron is deposited at one electrode. Determine the formula of the chloride of iron in the original solution.
c)Write the balanced equation for the overall reaction that occurs in the cell.
d)How many liters of Cl2(g), measured at 25oC and 750. mm Hg, are produced when the cell operates as described in part (b) ?
e)Calculate the current that would produce chlorine gas from the solution at a rate of 3.00 grams per hour.
Sr(s) + Mg2+(aq) ® Sr2+(aq) + Mg(s)
3. Consider the reaction represented above that occurs at 25oC. All reactants and products are in their standard states. The value of the equilibrium constant, Keq , for the reaction is 4.2 x 1017 at 25oC.
a)Predict the sign of the standard cell potential, Eo, for the cell based on the reaction. Explain your prediction.
b)Identify the oxidizing agent for the spontaneous reaction.
c)If the reaction were carried out at 60oC instead of 25o, how would the cell potential change? Justify your answer.
d)How would the cell potential change if the reaction were carried out at 25oC with a 1.0-molar solution of Mg(NO3)2 and a 0.10-molar solution of Sr(NO3)2 ? Explain.
e)When the cell reaction in (d) reaches equilibrium, what is the cell potential?
My favorite science podcast is ShortWave, a daily (about) 10 minute program on what’s going on in lots of different fields of science right now.
Go to: https://www.npr.org/podcasts/510351/short-wave (or listen however you get your podcasts) and browse the episodes. Choose one that sounds interesting and listen.
What was the name of the episode?
What was an interesting thing you learned?
Choose two more of the following science programs (no, I don’t listen to all of them) and choose one podcast from each. For each, answer the following questions. For many you have to go back to older episodes if you don’t want to listen to a coronavirus episode.
Feel free to listen to more than 2 more!
What program did you choose?
What was the name of the episode?
What was one interesting thing you learned?
What was your favorite program? Why?
- Scientific American: 60 second science – The episodes are actually about 5 -10 minutes - very short, interesting, current science stories
- The Disappearing Spoon (also a great book) with Sam Kean – about 20 minutes of science history stories
- Royal Society of Chemistry – The history and uses of each element in under 10 minutes
- Science Rules! with Bill Nye – 20-40 minute science explanations
- American Innovations – The stories behind discoveries in 20-30 minutes
- Science Magazine’s weekly podcast – Each is about 20-30 minutes
- Big Picture Science – Stories of science research in 50 minutes
- Stuff to Blow Your Mind – Stories of invention in about 1 hour
ELECTROCHEMISTRY
https://www.youtube.com/watch?v=teTkvUtW4SA
Tyler Dewitt - Introduction to Electrochemistry
https://www.youtube.com/watch?v=7b34XYgADlM
Tyler Dewitt – Galvanic Cells (Voltaic Cells)
https://www.youtube.com/watch?v=2VT5rl8P84M
Professor Dave - Electrochemistry
New Al battery
http://www.iflscience.com/technology/new-aluminum-battery-charges-minute
Article you might find interesting.
Electrochemistry is the study of the interchange of electrical and chemical energy. This means you can use a chemical reaction to produce an electric current and you can use an electric current to produce a chemical change.
Oxidation –
Reduction –
Half Reaction –
Galvanic Cell – A device in which chemical energy is changed into electrical energy due to a spontaneous redox reaction. There are separate chambers for oxidation and reduction.
Oxidation
Reduction
Half Reaction
Called
Mass of Metal
+ or –
The red cat gets fat
An Ox and Red Cat
Electrons Flow:
Ions Flow:
Cell Potential (E) – This is the force “pulling” the electrons from the oxidizing half-cell to the reducing half-cell, measured in volts.
Standard Reduction Potential (E˚) – Measured compared to Hydrogen with 1M solutions.
For oxidation, reverse the reaction and change the sign. However, we do NOT multiply or divide the voltage if we multiply or divide the half-reaction.
The potential for the electrochemical cell is the sum of the potentials of the oxidation and the reduction reactions.
Ox Zn ® Zn 2+ + 2e- +.76v
Red Cu2+ + 2e- ® Cu +.34v
+1.10v
Electrons lost = Electrons gained
Spontaneous = + E
Ex. Cu and Fe
Ag and Fe
Zn and Fe
Voltaic Cell Simulation
https://chemdemos.uoregon.edu/demos/Electrochemical-Cells-Computer-Simulation-Voltaic-Cells-Zn-Cu-Ag
Faraday (F) – is the charge on one mole of electrons = 96500 coulombs/mol (C = coulomb = the quantity of electricity transferred by a current of 1 amp in 1 second).
The cell potential (E) is related to the free energy difference (∆G) for a chemical reaction. (Reminder: Volt = J/C and n =mol of e-)
∆G = -n FE
Ex. Is the reaction Cu2+ + Fe ® Cu + Fe2+ spontaneous (+E and -∆G)? ∆G?
The E depends on Solution Concentration!
If the change in concentration favors the forward reaction, E increases.
If the change in concentration favors the reverse reaction, E decreases.
This is NOT an equilibrium system! DO NOT USE LE CHATELIER!
https://www.youtube.com/watch?v=jousNNceCXs
Organic Chemistry Tutor – Nerst Equation Explained
The Nernst Equation is used to calculate E for a cell at nonstandard conditions.
E = E˚ - 0.0592 log Q
N
- When Q =1, the potential difference between the two half-cells causes electrons to flow from one to the other, and this the driving force for the reaction. Under these 'standard' conditions, the cell voltage is described as having the 'standard' value.
- When Q > 1, relatively large concentrations of products and relatively small concentrations of reactants are present. This combination hampers the forward reaction, and the cell voltage is found to be less than the standard value.
- When Q < 1, relatively large concentrations of reactants and relatively small concentrations of products are present. This encourages the forward reaction, and the cell voltage is found to be greater than the standard value.
3 Mn2+ + 2 Al ® 3 Mn + 2 Al3+
Predict whether the E is larger or smaller than E˚ when:
(a) [Al3+] = 2.0 M and [Mn2+] = 1.0M
(b) [Al3+] = 1.0 M and [Mn2+] = 3.0M
(c) [Al3+] = 1.5 M and [Mn2+] = 0.5M
What to say…
An increase in cathode ion increases the driving force to produce voltage, a decrease in cathode ion decreases the drive to produce voltage
An increase in anode ion decreases the driving force to produce voltage, a decrease in anode ion increases the drive to produce voltage
A smaller reaction concentration produces a smaller driving force for the forward reaction, which produces a smaller cell potential.
A smaller reaction concentration increases the value of Q, which produces a smaller cell potential.
For any cell as the cell discharges, the concentrations change (reactants decrease and products increase). The cell discharges until the reaction reaches equilibrium E = 0 and ∆G = 0. At this point the battery is dead.
Electrolysis
https://www.youtube.com/watch?v=dRtSjJCKkIo
Tyler DeWitt - Electrolysis
An electrolytic cell uses an electric current to make a nonspontaneous redox reaction to occur. The amount of chemical change that occurs depends on the amount of current and how long that current (amps) flows.
Electrolytic Cell simulation
http://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/html5/Electro/Electro.php
Electrolysis http://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/html5/Electro/Electro.php
Reminder: 1 amp = 1C/sec
This calculation is all unit conversions.
Ex. What mass of copper is plated out when a current of 10.0 amps passes through a solution containing Cu2+ for 30 minutes?
- Convert amps and time in seconds to coulombs
- Convert coulombs to Faraday to mole of electrons
- Use moles of electrons to calculate moles of Cu formed
- Convert moles of Cu to grams of Cu
Ex. How long must a current of 5.00 A be applied to a solution of Ag+ to produce 10.5 g of Ag metal?
PRACTICE:
1.Consider ONLY the following half-reactions for Question 1:
HALF-REACTION Eo (V)
Al3+ (aq) +3e- ® Al (s) -1.66
Ni2+ (aq) + 2e- ® Ni (s) -0.25
Sn2+ (aq) + 2e- ® Sn (s) -0.14
Hg22+ (aq) + 2e- ® 2 Hg (l) +0.79
Ag+ (aq) + e- ® Ag (s) +0.80
Ce4+ (aq) + e- ® Ce3+ (aq) +1.61
__________a) Which species (specific ion or atom) is the weakest oxidizing agent in the list?
__________b) Which species is the strongest oxidizing agent?
__________c) Which species is the strongest reducing agent?
__________d) Which species is the weakest reducing agent?
__________e) Will Sn(s) reduce Ag+(aq) to Ag(s)? (yes or no)
__________f) Will Hg(l) reduce Sn2+(aq) to Sn(s)? (yes or no)
___________________g) Name all of the ions (on this list) that can be reduced by Sn(s).
___________________h) Name all of the metals (on this list) that can be oxidized by Ag+(aq)?
i)What reaction leads to the maximum positive standard potential? Indicate the Eonet. Write the balanced net ionic equation.
j) If the Ni2+(aq)/Ni(s) half cell is combined with the Hg22+(aq)/Hg(l) half cell, write an equation for the spontaneous reaction that occurs. What will be its standard potential?
k) Write the spontaneous reaction that occurs when the half-reactions Ag+(aq)/Ag(s) and Ni2+(aq)/Ni(s) are combined. What is the value of Eonet for this reaction?
2. In an electrolysis cell, a current of 0.250 ampere is passed through a solution of a chloride of iron, producing Fe(s) and Cl2(g). (The formula for the chloride of iron is meant to be ambiguous. See (b) below)
a)Write the equation for the half-reaction that occurs at the anode.
b)When the cell operates for 2.00 hours, 0.521 gram of iron is deposited at one electrode. Determine the formula of the chloride of iron in the original solution.
c)Write the balanced equation for the overall reaction that occurs in the cell.
d)How many liters of Cl2(g), measured at 25oC and 750. mm Hg, are produced when the cell operates as described in part (b) ?
e)Calculate the current that would produce chlorine gas from the solution at a rate of 3.00 grams per hour.
Sr(s) + Mg2+(aq) ® Sr2+(aq) + Mg(s)
3. Consider the reaction represented above that occurs at 25oC. All reactants and products are in their standard states. The value of the equilibrium constant, Keq , for the reaction is 4.2 x 1017 at 25oC.
a)Predict the sign of the standard cell potential, Eo, for the cell based on the reaction. Explain your prediction.
b)Identify the oxidizing agent for the spontaneous reaction.
c)If the reaction were carried out at 60oC instead of 25o, how would the cell potential change? Justify your answer.
d)How would the cell potential change if the reaction were carried out at 25oC with a 1.0-molar solution of Mg(NO3)2 and a 0.10-molar solution of Sr(NO3)2 ? Explain.
e)When the cell reaction in (d) reaches equilibrium, what is the cell potential?