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Mole City: Moles and Conversions in Chemistry

One of the most difficult early chemistry concepts for many people is the idea of moles and converting moles to other quantities.

Unfortunately, this is a fundamental part of chemistry.

Fortunately, there are a few ways to break it down easily. One of the methods that seemed to work is the "Mole City" diagram. It was how my chemistry teacher taught it and it's stuck with me every since.

The mole is a unit for measuring the quantity of an element. It "carries" us between different units of measurement.

So in our diagram, the "mole" is our train station. We can use this train to get between units.

If we want to get to "grams," we use molar mass as the conversion factor. The molar mass conversion factor is the "train" that takes us from "moles" to "grams."

If we want to get to "particles," we use Avogadro's number. Avogadro's number is the train that takes us between "moles" and "particles.

Sometimes, chemistry problems will give a quantity in grams and ask for the number of particles. But there's no "train" between "grams" and "particles." So first, we have to use "molar mass" to get to moles and then use Avogadro's number to get to "particles."

This is a highly visual representation of mole conversions. I will try to make a video or diagram to upload and explain this concept further.


there is another "train", used by gases, whose concentration expressed in moles can be converted into Liters, at Standard Temperature and Pressure. The conversion factor is the ratio between 1mole of gas (any gas) and its volume at STP (22.4L)


Francis M.

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