A
B
C
D
E
100
What is electrochemistry?
Electrochemistry is the branch of physical chemistry that studies the relationship between electricity, as a measurable and quantitative phenomenon, and identifiable chemical change.
100
What is electronegativity, and how does it contribute to creating a voltaic cell?
Electronegativity is defined as the tendency of an atom to attract or lose electrons. More electronegativity means more possibility of attracting electrons, and less means more possibility of losing electrons. It contributes to creating a voltaic cell because it will define which is the cathode and which is the anode, depending on the element’s electronegativity.
100
Name 5 everyday things we use that work through electrochemistry/ a redox reaction.
Batteries, remote control, cellphone, clocks, etc..
100
What is the ionic net charge of the anode?
The anode is the negative pole in a reaction, and the oxidation takes place there, so it keeps losing electrons, and the charge becomes positive
100
Where does the process of oxidation occur?
at the anode
200
How do electrochemical cells work?
By producing a electric current from energy released by a spontaneous redox reaction.
200
Explain the process batteries take to produce electric current
The electrons from the anode flow through the electrolyte into the cathode that reduces, whereas the oxide.
200
What does a substance go through when they lose electrons?
oxidation
200
What is a cathode?
It is the positively charged electrode by which electrons enter an electrical device.
200
Write half reactions for the redox reaction:
Au+3 + I- → Au + I2
300
why don’t copper and zinc create an electric current without the lemon?
Copper and zinc can’t go through a redox reaction alone because the electrons cannot flow, there is no channel to. The citric acid in the lemon acts as an electrolyte and allows the electrons to move freely, thus creating a battery.
300
State the three elements needed for a battery to work
An electrolyte that creates a bridge for the ions to transfer and two electrodes: a cation and an anion.
300
Which of the two is oxidation?
4HCl + O2 → 2Cl2 + 2 H2O
H2 + Br2 → 2 HBr
4Cl + O2 → 2Cl2 + 2 H2O is oxidizing because it loses electrons.
300
Describe what non-spontaneous and spontaneous reactions are
A non-spontaneous reaction is a reaction that goes against (-) the formation of products, it needs to be endothermic and/or have a decrease in entropy.
A spontaneous reaction is a reaction that goes in favor (+) of the formation of products, it’s exothermic.
300
Compare and Contrast galvanic cells and electrolytic cells
A Galvanic cell converts chemical energy into electrical energy and uses power from spontaneous redox reactions.
An electrolytic cell converts electrical energy into chemical energy with the use of an external source and uses power from non-spontaneous redox reactions.
400
Can you find the electrical cell potential in the following reaction? How did you do it? Reaction:
2Al3+(aq) + 3Cu(s) → 3Cu2+(aq) + 2Al(s)
Oxidation= Cu [0] → [2+]
3Cu(s) → 3Cu2+(aq) + 2e-
Reduction= Al [+3]→ [0]
2Al3+(aq) + 2e- → 2Al(s)
EO= Eo red - Eo ox
EO= (-1.66)-(-0.34)
EO= -1.32 V
Non-spontaneous
400
Arrange the following oxidizing and reducing agents in order of increasing strength:
Reducing agents: Cl-, Cu, H2, H-, HF, Pb, and Zn
Oxidizing agents: Cr3+, Cr2O72-, Cu2+, H+, O2, O3, and Na+
Arrange the following oxidizing and reducing agents in order of increasing strength:
Reducing agents: HF< Cl- < Cu< H2 < Pb< Zn< H-
Oxidizing agents: Na+< Cr3+< H+< Cu2+< O2< Cr2O72-< O3
400
There are more problems with batteries working during winter times, why?
The main reason why batteries have problems during winter times is because of the cold weather. The efficiency of the battery decreases in cold temperatures.
400
How could you increase the electrical potential of a lemon battery to create a greater voltage?
To create a greater voltage in an experiment that is using a lemon as a battery, you could create a circuit that has more electrodes so the potential increases (more energy is produced).
400
Calculate the electric potential of the following equation…
Cr2O72−(aq)+6Br−(aq)+14H+(aq)→2Cr3+(aq)+3Br2(aq)+7H2O(l)
Eºcathode= 1.23 V
Eºanode=1.09 V
Eºcell= 1.23 - 1.09 → 0.14 V
500
Justify the process our batteries took to produce the electric currents
The electrons from the anode flow through the electrolyte into the cathode that reduces, whereas the oxide.
500
Argue whether it is the anode or cathode what contributes more to the flow of electrons (electricity flow/current)
The anode contributes more because it is what provides the actual flow of electrons towards the cathode. Without the anode there would be no oxidation and flow of electrons in an electric circuit. These are the ones that react chemically and give electrons for the circuit to work.
500
Argue what makes a lemon battery work, moreover, why don’t copper and zinc create an electric current without the lemon?
Copper and zinc can’t go through a redox reaction alone because the electrons cannot flow, there is no channel to. The citric acid in the lemon acts as an electrolyte and allows the electrons to move freely, thus creating a battery.
500
Analyze the following result that was obtained from an experiment where the electric potential of batteries with different fruits was measured: A grape battery´s electric potential was tested and the voltage obtained was 0.2 volts dc. Where does the energy to create this amount of voltage come from? Where are the electrolytes? How is the electrical current generated and why?
In the experiment, there are 2 electrodes and one electrolyte. The electrode with the highest electronegativity (cathode), will gain the electrons from the anode. The electrons that are clumping up in the anode, will pass through the wire and travel from the anode to the cathode, but the protons are way too big to pass through the wire. This is why the electrolytes are used for. The protons will pass through the electrolytes. The electrolytes will oxidize the anode and positively charged ions will move into the solution. The electrons, now in the cathode, will take protons from the acid and reduce them.
500
Jimmy wants to determine by how much does a Lithium-Ion Battery lose its efficiency after 20 recharges. For his procedure, Jimmy first used an old Lithium-Ion battery from his broken phone. Jimmy only measured the voltage of the battery after 5 charges. After calculating the percent yield, he realized the battery was already 6.7% efficient. Because of this, Jimmy concluded that after 20 recharges a Lithium-Ion battery loses its efficiency by 100%. Evaluate Jimmy's Results, are they accurate? Can you create a better procedure?
Jimmy’s results are extremely inaccurate as there are many flaws in his procedure. The first flaw is that Jimmy used an already damaged and old Lithium-Ion battery. The second flaw is that Jimmy only measured the Battery’s voltage once. These two major flaws are what remove any validity from his results. In order to create a better procedure, Jimmy should use more than one fresh battery in order to account for error, he should measure the voltage of each battery at the beginning and periodically measure it every 2 to 5 recharges until he reaches 20. This will ensure that his data is accurate and correct.