Learn about Junior Chemistry, Balancing 2, in this comprehensive video by bannanaiscool.
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Let’s practice our balancing here with the combustion of a natural gas component called ethane. When you see methane or ethane or any kind of compound that has carbon and hydrogen in it and only those two that’s called Hydrocarbon. So when hydrocarbons undergo burning or combustion you always put down plus O2. That means hydrocarbon undergoing combustion called hydrocarbon combustion and you always get if the combustion is complete and proper two chemicals that are formed—carbon dioxide and water. Those are the things that are produced from hydrocarbon combustion. Actually I wasn’t kidding there when I went (makes sounds) because when we eat sugars we actually take chemicals that are very hydrocarbon in nature into our bodies and produce carbon dioxide as waste product and water in order to make energy for our bodies. And by the way we breathe in an oxygen too to be able to cause that reaction to take place. It’s not combustion in our bodies, we’re not burning them in ourselves but actually you’ve heard about us burning energy. So there you go. Now here’s that ethane undergoing combustion with carbon dioxide and water—products, reactants. So let’s balance this equation. Two carbon, one carbon so put two in front. Six hydrogen—we just go consecutively through. Six hydrogen so what do we do here, there are two there? Put the three in front, that’s good. Okay, now for the oxygen well we've got two on this side and let’s go over to this side. Now be careful there’s not two there, there is two times two there which is four. But there is no four on this side, there’s more. There’s a plus—these many oxygen over here. Now get this, two times two is four plus three times one, that’s water-gas there—water vapor. That’s three plus four that’s seven oxygen. What times two is equal to seven? Well 3.5 times two is 7. You can put 3.5 in front here. You could also put seven over two. Seven over two times two—two is canceled and you're left with seven, you get it? Some people are going to look at this and say I don’t like that because it’s not balance, and that’s right. So therefore if you want to balance that using lowest whole number ratio, everyone of those numbers we put in front and multiply it by two. So this one here, so that’s a two. Now with seven halves that’s a seven and this number here of course before was a two so we make that four. This number here is a three and we make it a six—2, 7, 4, 6 is the lowest whole number ratio for balancing that called hydrocarbon combustion. Now let’s go along to some replacement reactions.