Week Seven: Molecular Weight

Inert Gas of the Week: Nitrogen

An inert gas is a gas that is non-reactive in normal circumstances. Nitrogen is ubiquitous. It constitutes nearly 80% of the earth's atmosphere. It is also in every living organism in the form of amino acids, which are the building blocks of life. (I wonder why something that is so non-reactive shows up so many places? A bit counterintuitive).

Like other inert gases (being the lazy, couch-potato elements that don't want to get up and react) nitrogen is used to prevent unwanted chemical reactions. It is used in food packaging because bacteria and fungus cannot flourish without reacting with gases. In addition, it won't permit any reactions to occur within the food, thus preventing any change in the quality of the food in transit. I'm surprised they don't have nitrogen creams to smear on people's faces to prevent oxidation and aging! With meat, at least, nitrogen sort of tweaks an arrow of time. But oops, that's physics class.

A cool thing (pun definitely intended): liquid nitrogen is a cryogenic liquid. At atmospheric pressure, it boils at −196.5 °C Very cold. It's like dry ice. It is used as a regfrigerant. I know this because my old refrigerator just got filled up with nitrogen which really gave it a new lease on life. It is used to cryogenically freeze blood and other things like reproductive cells and maybe even organs.

Avogadro's Hypothesis

I found this exercise to be somewhat intersting but a little irritating. I still don't see why a well tested hypothesis isn't a law (but appears to become a theory, as if that distinction meant something to me. This made me get number 1 wrong. I hate multiple choice questions that turn on phrasing rather on whether you actually understand the concept. But, I hear that's what the licensing exam is all about.

Moles

I found the link helpful, but overall I thought the handout in class is better at getting to the relevance of the mole concept. The link deals more with the history and with the details of the concept. I find that with this type of thing, it's better not to think about it too much. Getting the general principle that a mole is like a dozen is the key. It's just a number and you can apply it to whatever. That's my take home point.