UNC Chemistry Experiment Four Learning Objectives Question

Using full details and ample evidence, create a reflection paragraph that describes four learning objectives you met while performing this experiment.  View the learning objectives from the lab manual provided and select four to focus your writing on.

Virtual Lab Manual
Redox Reactions: Discover how
batteries work!
Synopsis
Oh no! Your electric car has broken down. Can you build your own battery to get moving again?
Discover the chemical reactions that power batteries by finding oxidation numbers, balancing
redox reactions, and experimenting with redox reactions in the lab, then make a
recommendation to your friend Hansen about whether to replace his worn-out lead-acid
battery with a new lithium-ion one.
Oxidation number and redox reactions
Join Dr. One in the redox chemistry lab to find out how redox reactions power batteries. Start
by using the periodic table to predict the oxidation numbers of various compounds. Then
balance the charges of half-reactions and see what happens to the oxidation numbers when
electrons are lost or gained!
Redox potentials and balancing reactions
Develop and test a hypothesis about the reaction between copper and different aqueous
solutions based on their reduction potentials. How can these potentials help you predict the
direction of a redox reaction? Batteries can be both acidic and alkaline, so next up, join Dr.
One to balance redox reactions one step at a time in both environments.
Optimize a galvanic cell
Now that you understand what a redox reaction is and what happens to the electrons, learn
how this can be used to generate power in a galvanic cell. Experiment with different
combinations of metal for the anode and cathode to find the most powerful duo. Will you be
able to complete the reactivity series and discover another way of predicting the direction of
redox reactions? Remember that you set out to find the best kind of battery to fix the electric
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car. With everything you now know about galvanic cells, what kind of battery do you
recommend to your friend?
Learning Objectives
At the end of this simulation, you will be able to…
● Describe the concept of oxidation states and explain trends in the periodic table
● Apply the rules for determining the oxidation state
● Describe the role of the electron in reduction-oxidation
● Predict the direction of redox reactions
● Balance a redox reaction in both acidic and alkaline environments
Techniques in Lab
● Aqueous redox reactions
● Galvanic cells
Theory
Redox reactions
The term redox is a combination of the words reduction and oxidation. It refers to all
reactions that involve the transport of electrons from an electron donor to an electron
acceptor. A molecule that gets reduced gains electrons, and loses electrons when it gets
oxidized (see Figure 1). For a redox reaction to occur, a molecule has to be reduced by another
molecule that gets oxidized.
Figure 1: Redox reactions
OIL RIG is a common mnemonic to remember which is the oxidation and which is the
reduction: Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons).
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In biological systems, redox reactions are critical for cellular respiration. In the cell, electrons
are often transferred via electron carriers, molecules that accept electrons from one
molecule and transfer them to another.
Galvanic cells
In a galvanic cell, the oxidation half-reaction occurs at the anode. Since electrons are
deposited on this electrode, it is the negative electrode. The reduction half-reaction occurs
at the cathode, which loses electrons and is therefore the positive electrode. The two halfreactions are physically separated, which forces the electrons to move through an external
circuit (see Figure 2). This is what generates electricity.
Figure 2: Galvanic cell with two half-cells, external circuit (wires) connecting the anode and
cathode, a voltmeter for measuring the cell potential, and a salt bridge.
To allow the reaction to continue, the charges need to be balanced and ions need to be able
to move between the cells. Without this movement of ions, one half of the cell would build
up a net positive charge and the other half would build up a net negative charge and the
reaction would stop. Both anions and cations contribute to the balancing of the charge and
the completion of the electric circuit. In a galvanic cell, the ions can move through a salt
bridge (see Figure 2) or a porous membrane between the two half-cells.
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2020
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