Learn about Junior Chemistry, Balancing 1, in this comprehensive video by bannanaiscool.
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Rob Lederer: Now you know then there are elements. When they react together, they form these compounds and we can write chemical equations to be able to describe what's happening. So, equations are when we take chemicals that are reacting that is called reactants and they produce things that are called products. We can write these chemicals down in formulas, write our chemical equations to be able to describe what's happening. So, now in this question, I've going to have the board here. Let's take some phosphorous and react it with chlorine, so it's two non-metals coming together to form a molecule and let's make that molecule phosphorous pentachloride. So, start with that. We got some phosphorous, we got some chlorine and we are going to make that product over here on the other side of that arrow, this means produces; right, this means reacts with. So, did you notice this thing, right? This is not good. I'll tell you why. Phosphorous is not P. you have to write the elemental form that occurs naturally in nature in these types of reaction. So, P4 reacts with Cl, no group seven, CL2. So, it's P4 plus Cl2. Now, what does that make? It can make a compound called phosphorous pentachloride and that's actually a solid at room temperature. This is a gas and this is a solid too. You kind of have to be told with these molecular ones whether they are solid or liquid or gas, but listen to this. All ionic compounds when we make them, they are solid at room temperature, unless you put them into the water, and then turn aqueous. P4 plus Cl2, when they get together, they get 4PCl5. but, there is still 4CPs that are reacting, but only one produced. We have to balance this equation. How do we do that? Well, we put numbers in front to describe the balancing and these numbers are actually, it represents the number of moles. Well, we get to moles in a while and I'll tell you what they really mean. Right now, they are just these balancing numbers or coefficients that we put in front. For instance, if we've got four phosphorouses here, we have the potential to be able to make, I am going to move this over a little bit. Sorry. We have the potential to make four phosphorous compounds here. So, P4 here, we need four over here. We don't put a four there, we put it in front. It's coefficient. So, we can have four of these compounds, but look what this is saying. Two chlorines made how many here, well not five, but four times five, which is 20. That's not balanced. How do you balance it? Well, if there is four times five, 20 chlorines here, what times two is going to be able to get us 20 chlorines on this side? Pretty obvious I hope, but the answer is ten. Ten times two, that's 20 chlorines,. Now, look at the way this is balanced. Four phosphorous here, four phosphorous here. Ten times two, that's ten chlorine molecules is 20 chlorines atoms. Four times five is 20 chlorine atoms and this one ten and four, we don't put the one there. that's the balanced equation for this reaction. Okay. And this one is called simple composition, because we are just taking elements and making the compound. Now, let's do decomposition. Take this compound, iron three oxide. Now, why is it iron three oxide. There is only two irons here. What's the charge originally of Fe? It was a three positive and the O is two negative. So that's the iron with the three positive charge, iron three oxide. Iron two oxide, we have that formula, FeO. Okay, now, if this chemical, I would tell you that it decomposes into its elements. How do you write that as an equation, and then how do you balance it? If Fe2O3 decomposes, we don't write Fe2 and then plus O3. No. we write down what the elements are in their natural states found out here. Iron is just Fe. Then it's a salt because iron doesn't melt, isn't it? And then plus oxygen, but oxygen is O2, no group seven, it's diatomic. Now, that's iron three oxide decomposing into its two elements. Now, we are going to balance the equation. Okay, watc