WEBVTT
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give it a description of a chemical reaction. This
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could be written as a balanced chemical equation, which
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can then be interpreted in several different ways. So
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if, for example, we have solid tetro,
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phosphorus try sulfide reacts with oxygen gas to form solid
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tetra phosphorus dick oxide and sulphur dioxide gas. Our
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first step is to write the chemical formulas for each
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of these substances. Tetra phosphorus try sulfide contains phosphorus
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and tetra means four, and sulfide is so for
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, and there are three because of the try two
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solid plus oxygen gas in the chemical reaction. Oxygen
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gas is always+02 and it forms solid tetra phosphorus
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. So again, P four Decca oxide deca is
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the prefix for 10 plus sulphur dioxide, which is
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one sulfur and to Oxygen's. This is a gas
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, and this is a solid. Once we've written
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our skeletal equation, we can balance the equation by
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changing the coefficients we see on this side. Therefore
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, phosphorus is on this side. There for phosphorus
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is here. There are three suffers, and here
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there's only one, so we multiply by three.
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This gives us 10 oxygen's plus three more here for
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a total of 16 So that means the coefficient here
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has to be eight. So now we have a
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balanced equation, and we can interpret this in several
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different ways. If we think of it. In
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terms of molecules, this equation tells us the ratio
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of molecules that will form. So, for example
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, if we have one molecule of P for s
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three, it will react with eight molecules of oxygen
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to form one molecule of P for 0 10 and
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three molecules of sulfur dioxide. So the coefficients from
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the balanced equation can tell us how many molecules react
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with each typically because we don't do reactions and molecules
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, they're too small to measure out. We use
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moles instead. On this equation can also describe the
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number of moles required. So, for example,
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the coefficients tell us that one mole of P for
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S three we'll react with eight moules of 02 to
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form one more p for 0 10 and one mole
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of sulfur dioxide so it can be interpreted in terms
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of other molecules or moles. The third way that
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we can consider it is to look at it in
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terms of mass in the law of conservation of mass
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as well as the relationship between mass and moles.
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In order to do this, we need to know
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the molar mass of each substance. And so we
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find that by using the periodic table So one more
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of P four s three has the molar mass before
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times the molar mass of phosphorus, plus three times
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the molar mass of sulfur, or 200 and 20
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point 093 grams. Similarly, we confined the molar
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mass of oxygen to be 31 0.998 grams by adding
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two times 15 and the molar mass of P for
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0 10 is equal to 200 and 83 0.886 grams
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. And finally, the molar mass of sulfur dioxide
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is equal to 64 0.58 grams. And so we
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can interpret this equation in terms of grams by multiplying
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the molar mass by the coefficient in front of the
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equation. So we multiply this number by eight in
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this number by three, and these still are multiplied
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by one. So for the reaction, I need
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to have this many grams of each substance, and
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I could describe the reaction in terms of grams so
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it would be 220 grams of p for S three
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reacts with 255 went 984 grams of oxygen to form
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283 grams of P for 0 10 and 192 0.174
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grams of sulfur dioxide.