Breaking Bad : Season 1 : Episode 3 : “And the Bag’s in the River”
With practical issues (such as last week’s acid disaster clean-up) and character development dominating this episode, science takes a bit of a back seat. In this post, I’ll be talking about the composition of the human body and redox reactions.
The human body
As Walt and Jesse struggle through their clean-up operation (neutralising the acid with baking soda, which is also a good cleaning/scouring agent), Walt has a body-components-inspired flashback. His plan to disassemble the body into its constituent parts worked, more or less, and those parts (according to his assistant and the blackboard) were:
|Chlorine||0.2||Actually reckoned to be 0.025 mol %|
|Sulfur||0.050002||Actually reckoned to be 0.06 mol %|
This adds up to 99.980042 mol %. Walt says it’s 99.888042 mol %, proving that it pays to have a calculator around. The remaining 0.019958 mol % (or 0.111958 mol %) thus accounts for the soul (or for elements they missed like potassium and iodine, or for trace elements like manganese and zinc, or for experimental error).
You may have read that the human body is around 65 % oxygen, 18 % carbon and 10 % hydrogen. These values are by mass, whereas the values that Walt writes down are by moles.
For background information on this topic, see the primer on molar quantities.
If Walt’s students weren’t watching videos about carbon, according to what’s written on the blackboard they’d be exploring redox reactions – very common chemical reactions that have certain characteristics. Redox is an abbreviation for reduction / oxidation, which tells us that one reactant is reduced and another is oxidised:
- Oxidation: Gain of oxygen and/or loss of hydrogen and/or loss of electrons
- Reduction: Gain of hydrogen and/or gain of electrons and/or loss of oxygen
As usual in chemistry, things must balance out. If something is oxidised, something else must be reduced and vice versa. There are a couple of examples on the blackboard – on the left-hand side, we can see:
CH4 + O2 → CO2 + H2O
This is a chemical equation for the combustion of methane (CH4) in oxygen (O2) to give carbon dioxide (CO2) and water (H2O), and is a typical example of a redox reaction. Carbon both loses hydrogen and gains oxygen, so it is being oxidised. Oxygen gains hydrogen, so it is being reduced.
As written, the equation shows where the oxygen and hydrogen go from and to, but does not balance. It should be:
CH4 + 2O2 → CO2 + 2H2O
On the right-hand side, we can see:
H+ + Cr2O72- + C2H5OH → Cr3+ + CO2 + H2O
This is another redox reaction – potassium dichromate (K2Cr2O7 – this is an ionic salt, meaning that the K2 and Cr2O7 components separate in solution to give 2K+ and Cr2O72-) reacts with ethanol (C2H5OH) in the presence of acid (H+) to give chromium ions (Cr3+), carbon dioxide (CO2) and water (H2O). Chromium loses oxygen, so it is being reduced. Carbon loses hydrogen and gains oxygen, so it is being oxidised. The potassium (K+) is not involved in the reaction, so Walt didn’t bother to write it down.
You may have noticed that the equation above also does not balance (perhaps Walt started it in one class and planned on finishing it before Emilio got in the way). It should be written:
16H+ + 2Cr2O72- + C2H5OH → 4Cr3+ + 2CO2 + 11H2O
For background information on this topic, see the primer on redox.
Elements in the credits
|STeven Michael Quezada||Tellurium|
|Robb Wilson King||Tungsten|