The Good Teacher

376  Electrolytic Chemical Reactions

Yohn questioned his life often, nowadays - surprisingly, even more than when he had to live a life drenched in darkness. After a faint light was split on his black canvas, thanks to the Magi-Core, Yohn took the initiative to pull apart the curtains so that he could finally let all the light in. However, in this process, he had taken on two hangers-on.

Well, calling them hangers-on would be a disservice, since they were contributing a lot to his endeavour to step into the light. The fact of the matter was that their mere presence increased the pressure bearing down on Yohn. He felt that with the two people on board, he just HAD to succeed or else he would be a complete failure of a mage. Not that either of his two "partners" had explicitly stated that to him.

"You look distracted," Senior Brother Markus said from Yohn's side causing him to flinch involuntarily.

"I was just thinking," Yohn responded while picking up the pace as they walked towards the Chemistry Lab.

"Care to share what you were thinking about?" Markus probed, to which Yohn just waved his hands and dismissed, "It's nothing serious."

Markus shrugged in acceptance. If it was a trivial matter, there was no point in digging into it, especially since they had arrived at their destination. Upon entering the lab, they were greeted with a barren room filled with a maze of empty tables. A few near the centre were populated with equipment and apparatus, and standing next to them was the sole figure of the Sect Leader.

"I did not think I would have to requisition a lot of this chemistry equipment just yet. My plan was to But you ambitious kids have proven me wrong once again!" He exclaimed with a smile. "Come, come! I have prepared the experiment for today."

The duo walked through the maze-like desk arrangement, towards the Sect Leader.

"Did you get a chance to read what I asked you to?" The man asked.

Both Yohn and Markus both nodded hesitantly. They could only hit the first two books in the exhaustive list, which was already a grand achievement since it covered some topics that had a lot of "just take my word for it" feel to it since they could not verify them with experiments. For instance, reversible reactions and equilibria were still in the realms of myths for the duo, since they just did not have a way to verify the so-called Haber Process.

"While I'd love to take my time and cover everything you need to know about redox reactions, I'm sure you two don't have the patience to sit through that long lesson which will inevitably span weeks," the Sect Leader commented. "So, I've decided to compress it down and only focus on what you need to know."

"We'll start by showing a simple electrolysis process. What I have here is distilled water with pure salt dissolved in it, as well as a few droplets of red cabbage juice which is why it has such a faint purplish shade," he said while pointing at a glass beaker in front. "In the beaker, I have placed two graphite rods. These rods will be connected to a positive and negative terminal of a power source. For this experiment, I will be acting as this source."

The graphite rods had a cable coming out of the unsubmerged ends that were each held in one hand by the Sect Leader.

"As you know, when salt dissolves in water, the ions dissociate. The positively charged sodium ions, the cation, and the negatively charged chloride ions, the anion, dissociate fully. Water is also in a state of partial dissociation, with hydrogen cations and hydroxide (OH-) anions. Since the solution is filled with ions and can conduct electricity, it is called an electrolyte. When I provide a charge to these electrodes, with the one connected to the negative terminal called the cathode and the positive terminal the anode, the circuit gets completed through the electrolyte, and electrolysis takes place."

"What is electrolysis? When the anode gets charged with a positive charge, it is basically a terminal with electron deficiency. This deficiency attracts the ions in the solution that have an electron surplus. As we know, this solution has two such anions: the chloride and hydroxide ions. Technically, both of them can be drawn towards the anode, however, we can see here that there is a faint yellow gas being released from the surface. This is an indicator that chlorine is being released - which means that it is the chloride ion which is reacting. Since an electron is being lost, it is oxidation that takes place at the anode. You must be wondering why it is the chloride and not the hydroxide ions that are being oxidised. That has to do with the standard reduction potentials of the two ions. You can read up on them later."

The Sect Leader then nudged his head towards the cathode and said, "On this electrode, we have reduction taking place, where the electron abundance is being diffused with the cations reacting and taking them away. As you know, there are two cations in this solution. Which one is being reduced at the cathode?"

Markus raised his hand and said, "The hydrogen cation."

"How do we know that?" The Sect Leader asked Yohn.

"Because there aren't any sodium deposits at the electrode?" Yohn hypothesised.

"Correct! Once again, this has to do with the standard reduction potentials. Alternatively, if you think logically, the moment sodium forms in the cathode, it should automatically react with the water and become sodium ions due to its reactivity," the Sect Leader explained.

"So what is left in the electrolyte as the experiment continues?" He asked.

"Sodium cations and hydroxide anions," Yohn answered.

"The two ions in their dissociated state dissolved in water form sodium hydroxide, which we know to be a potent alkali." As he said this, the Sect Leader gestured at the solution which was changing colour from faint purple to blueish-green. "And there you have your proof. The natural pH indicator that we dissolved in the solution is showing an increase in basic properties of the solution."

"This is your crash course in electrolysis. It is the process of inducing chemical reactions using electricity," the Sect Leader narrated. "You have an anode and a cathode, with oxidation at the former and reduction at the latter. Of course, there is a prerequisite that the electrolyte contains ions for electrolysis to be possible. You cannot use oil or nonpolar solutions for electrolysis, since there aren't any ions in it. In that sense, electrolysis only works with ionic compounds (molten or aqueous), aqueous solutions and metals (molten)."

Scooting over to the next prepared experiment, the Sect Leader continued his explanation, "This here is a type of reaction in the same vein, but works opposite to electrolysis. Here, the chemical reaction generates an electric current. This was much harder for me to prepare because we needed very specific electrolytes. On the left beaker, have filled it with zinc sulphate, and on the right you have copper sulphate. In the zinc sulphate solution, I have dipped an electrode made of zinc. In the copper sulphate solution, I have dipped a copper electrode. Connecting the two is what you call a salt bridge. It's basically absorbent paper dipped in potassium chloride. Each electrode-electrolyte combination is a half-cell. Connecting the two electrodes with a cable completes the circuit which creates a full cell. Let me show you."

As the Sect Leader connected the cables together, Markus and Yohn could see chemical reactions taking place in each of the beakers. The Sect Leader separated the connecting cables slightly, and periodic sparks started to jump between the small gap.

"This is a voltaic cell. On the zinc side, you have oxidation taking place, as the zinc atoms from the electrode lose electrons and zinc ions get dissolved into the solution. The electrons get carried through the wire to the copper half-cell, which has a reduction taking place at the electrode. The copper ions in the electrolyte get attracted to the electron abundance at the electrode, and we have copper depositing there. This is just one type of voltaic cell. You can create a voltaic cell with other electrodes and electrolytes, but for it to generate a potential you need to confirm it against the standard electrode potential data table."

The Sect Leader turned towards Yohn and Markus, the latter of whom was furiously taking notes. "I know that this is a lot to digest all at once. I practically dropped a month's worth of information in an hour. BUT, this crash course should help you understand what you read till this point. However, I also realise that spending time to understand this topic just to fill in one blank in your experiment isn't proper utilisation of time and resources. So I took the liberty of preparing what you need to create the electric cell."

The Sect Leader pointed towards another table, which contained two stacks of copper and zinc plates with a container of acid, cables, and other miscellaneous items. He handed a rolled parchment, which unfurled to show a diagram.

"This is the schematic for a Voltaic Pile. It uses the same principles as what you saw just now. You should be able to build it and test it out by yourselves," he instructed. At that moment, Markus' hand rose.

"Master, do we really need to create a cell? Why don't you teach us the spell you used earlier when performing electrolysis?"

"That's something only I can do," the Sect Leader explained. "I used my special ability to warp my nature - essentially turning myself into a battery. You cannot do it. And before you ask me to become the battery for your experiments, let me tell you that you won't learn anything that way. Insights are best gained through trial, error and learning. You can take shortcuts most of the time, but not all the time."