WEBVTT
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given a description of a chemical reaction, we can
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take this description and write it in a balanced chemical
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equation by first identifying the formulas for the substances involved
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and then balancing by changing the coefficients. So,
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for example, when gallium metal is heated, an
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oxygen gas it melts and form solid gallium oxide.
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So we know that we're starting off with gallium metal
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. Gallium is an element, and when I looked
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on the periodic table, the symbol for gallium his
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G uh, it's a metal, so that means
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it's a solid. It reacts with oxygen gas.
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Oxygen is a dye atomic element, and so exists
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as 02 and chemical reactions. It reacts to form
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the substance. Gallium three oxide gallium three is an
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ionic compound with a plus three charge. An oxide
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is the oxygen, and I end with the minus
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two charge. And so the formula for the neutral
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compound is G A to 03 So the product his
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g A to 03 which is a solid. So
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this is called our skeleton equation. Where we have
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the substance is written up the balance We changed the
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coefficients. I am one gallium on this side and
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two on this side have to oxygen's here and three
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accidents here. So I look for the lowest common
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multiple of the oxygen's, which means that I have
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to multiply this side by two on this side by
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three. So now I have six Oxygen's on both
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side, three times to and two times three.
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It's also changes the gallons on this that have two
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times two or four, which means I need to
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have four gallons here. So the balanced equation is
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for G A S plus 3+02 g makes two
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g A 203 s. A second example has liquid
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heck sane burning an oxygen gas to form carbon dioxide
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gas and water vapor. You don't know what hexane
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is. It's a hydrocarbon, which means it has
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carbon and hydrogen. The heck sane is a six
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for carbon, and there are 14 hydrogen and this
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is a liquid. So we right l it reacts
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with oxygen, which again is oh to gas to
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form carbon dioxide, which is carbon with two oxygen's
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and water vapour. Water is H 20 and vapors
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. Another word for gas. These can be a
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little tricky to balance so we start with our carbons
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on this side. There are six, so put
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a six. Here there are 14 hydrogen is which
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would make me think a seven goes here seven times
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. Two. When I look at my oxygen's,
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I have 12 oxygen's plus seven or 19 oxygen's,
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which is an odd number. So over here I
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have a die atomic oxygen so I can put 19
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have in order to get 19. But I can't
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leave it like that because that's not a whole number
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. So I then go through and multiply everything else
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by two to get rid of that. So this
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should be a two, 19 12 and 14.
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The last example looks at ionic compounds. I have
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solutions of calcium chloride and sodium phosphate, and they
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make a solid calcium phosphate as well as a solution
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of sodium chloride. So I have different ionic compounds
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that I need to find the formulas for. So
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calcium chloride is made up of the C A two
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plus ion and the C L minus. I on
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or see a seal, too. Sodium faucet is
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the n A plus. Ion and phosphate is the
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poly atomic ion P o for three minus or an
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A three p o for calcium phosphate is see a
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two plus combined with P O for three minus or
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C a three p 04 two and finally an A
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C L is in a plus and C l minus
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or in a c. L. So to write
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the balanced equation, they have see a feel too
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, which is in solution. So we write a
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que plus on a three p a for also a
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quist solution or a que make solid calcium class fate
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. So see a three p o for two,
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which is a solid. So in parentheses, s
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plus a quiz and a meal. And when we
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look to balance, we can see on this side
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we'll start with their calcium. Is there are three
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calcium someone for three here, which makes six chlorine
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six here and the two here to balance the sodium
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and classmates