P1 (inner voice): dang it, my macbook is low on power again?? this thing used to last up to 9 hours!

P2: well, that’s because even secondary batteries degrade over time

P1: what the heck, how can you hear me?

P2: Your battery is dependent on a process called redox, a series of reduction and oxidation reactions that account for the gain and loss of electrons

P1: redox? oxidization? electrons?? and who even are you?”???

Galvanic Cells(F2.5, F3.2)

P2: Let’s take your computer battery for example, which is probably composed of nickel-cadmium galvanic cells

P1: galvanic cells?? I thought cells were only in my body

P2: nope, galvanic cells are devices that transform chemical potential energy into electrical energy through the transfer of electrons, also known as reduction-oxidation, or redox for short, reactions. let’s draw it out:

• We start off with two beakers of electrolyte solution, a substance that when dissolved in water, conducts an electric current
• We then add a salt bridge, made from sodium chloride, which is the connection between our electrolyte solutions, or half-cells, allowing an ion current to flow
• Now, we can use a voltmeter, which will measure the electrical potential difference
• Each probe is connected to an electrode
  • Difference between the two electrodes is their polarity
  • The anode is negatively charged, and is where oxidation occurs, and where electrons are lost
  • The cathode is positively charged, and is where reduction occurs, and where electrons are gained
• It is important to note the direction of electron flow
  • Electrons flow from high to low electric potential
  • Negative charges will want to move away from the negative anode, and will be attracted to the positive cathode
• We can also note the direction of ion flow
  • Cations from the salt bridge will flow towards the cathode, due of negative electrons, while anions will flow towards the anode

When we thicken the electrolyte solution we get a dry cell; and when we connect many galvanic cells in series, we get a battery!

We’ll save this for later, when we go into the redox of it all.

Balancing Redox Reactions(F2.3)

P1: that’s cool, but how can we account for all the electrons being transferred?

P2: great question; let’s determine the half reactions and balanced equation to find out.