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Stoichiometry: Introduction to Moles (4 of 4) |
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You'll probably need to read the text on the right to answer the questions below.
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Many things have units associated with them. For football it's the yard, for sprinters it's the meter, and people who make donuts it's the dozen. Units are important because they give us a common understanding of distance, amount, time, and so on. This lets us meaningfully communicate with other people about our experiences. It would be weird to discuss a track star running a 100000000000 nanometer race. It would make more sense to us to say a 100 meter race. In chemistry we use the mole. This is because we often think in terms of atoms and molecules in chemistry. Since atoms are small we need a unit that represents a lot of them. Such a unit makes conducting experiments and making calculations more convenient. One mole consists of 6.02 x 1023 particles (atoms, molecules, etc.). Asking for one mole of NaCl is easier than asking for 602000000000000000000000 molecules of NaCl. All of this is helpful because it allows us to understand the amounts of reactants used and products created in chemical reactions. When we balance chemical equations we often think about the coefficients as moles since it shows us the ratio of reactants and products. You could think about chemical reactions in grams but it's more difficult and doesn't clearly show what is happening chemically.
Two moles of hydrogen molecules plus one mole of oxygen molecules yield two moles of water molecules. We can change the moles back to grams (using the GFM) when we want to weigh them on an electronic balance or scale. As a result, chemists often think about reactions in terms of moles but convert to grams when they need to weigh out a specific amount. |
