- Chemical reactions introduction
- Balancing chemical equations
- Balancing more complex chemical equations
- Visually understanding balancing chemical equations
- Balancing another combustion reaction
- Balancing chemical equation with substitution
- Balancing chemical equations 1
Relating the balanced chemical equation to the structural formulas of the reactants and products.
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- I'm confused on the Lewis Structures. How do you know where the atoms are? Like, how do you know where the hydrogen atoms are placed?(20 votes)
- That is too involved to answer here briefly. Here are some links that should help you.
If you have an example (but not homework) molecule you'd like me to show you how to find the Lewis structure for, I would be happy to go over that with you.(33 votes)
- At1:40, Sal used bonds with two lines and with one line. What is the difference, and why did he use them the way he did?(14 votes)
- It denotes single bond for one line and a double bond for two. Each line in a bond denotes an electron pair being shared.(14 votes)
- What's the difference between O_2 and 2O?(6 votes)
- O₂ is a single particle (a molecule) that consists of two atoms of oxygen.
2O represents two separate particles, each of which is an atom of oxygen.(16 votes)
- I don't understand the molecule structure. Why is he drawing it all out? It's familiar but not quite that easy to understand. Help me!(6 votes)
- Don't worry too much about the structure of the molecules just yet. For now, all you need to know is that the letters that Sal drew represent atoms in the molecule structure. For example the "C" he drew in the first figure represents one carbon atom. You can think of these letters as the LABELS of the atoms. The lines connecting the atoms represent bonds between the atoms. You can think of these lines (bonds) as stretchy rubber bands connecting each of the atoms. The number of lines indicate the type of bond connecting the atoms. As far as I know there are only three types of common bonds, single (one line), double (two lines), and triple (three lines). Of course, it gets more complicated from here with sharing electrons between atoms, and other stuff. If you want to read more about bonds and notation, click this link here: https://en.m.wikipedia.org/wiki/Chemical_bond.(11 votes)
- If the coefficient or subscript is their would there be double the atoms or does it just mean that there are two molecules of the product or reactants(5 votes)
- If the number is before the molecule, then you have two of those molecules, e.g. 2NaCl means two molecules of NaCl.
If the number is in subscript (small, bottom right) after an element, then that element is repeated twice, e.g. H₂O (water) means that the molecule has two hydrogen atoms and one oxygen atom.(13 votes)
- Why is balancing the reaction so important? How would you come up with the reaction in the first place?(4 votes)
- Because of the law of conservation of mass, balancing chemical equations gives a more accurate representation on what's happening in a reaction. The accuracy of the ratios of moles is important in calculating the theoretical yield and how much stuff is reacting mass-wise (stoichiometry).
There are many types of reactions. Synthesis, decomposition, single displacement, double displacement, and combustion are the main few. The type of reaction (and thus, the product(s)) can be predicted by looking at the reactants. Try searching "predicting chemical reactions" and see what comes up.(5 votes)
- Why does quick lime react with water and turn into slaked lime if both of the reactants are already stable on their own?(3 votes)
- Chemicals can be perfectly stable normally, but when presented with a pathway to go to even more stable state, with lower energy, then they tend to take that pathway. So even if quick lime is stable normally, when able to react with water, it will do so to turn into slaked lime because slaked lime has even lower energy compared to quick lime.
Hope that helps.(6 votes)
- if you need to balance the equations does that mean the equation that you started out with (C2H4 + O2 ----> H2O + CO2) is incorrect? Or are the unbalanced and balanced equations both right?(1 vote)
- A chemical equation that isn't balanced is called a skeleton equation. A skeleton equation isn't a wrong way to look at a reaction; it tells you what reacts to produce what. The only downside to using skeleton equations as opposed to balanced equations is that skeleton equations don't tell you the quantity of 'stuff' that reacts. Quantity becomes very important later in chemistry, so it is advised to always balance chemical equations.(9 votes)
- Sal said that c2o2 isnt a thing in nature but it is actually ethylene dione right?(3 votes)
- C2O2 is ethylenedione. However, it is purely theoretical, and if it existed, it would break down into CO within 0.5 nanoseconds, which would instantly null any preexisting source. There is also no natural process that replenishes ethylenedione, meaning any 'natural' formed C202 would have already decomposed before the creation of our solar system(which would be almost 4.5 billion years!)(4 votes)
- Why can't you right C2H4 as (2)C1H2? Isn't it the same compound by the ratios?(2 votes)
- If you write (2)C1H2, it will look like you are taking two moles of a compound C1H2 which does not exist in nature.
C2H4 (Ethene) is an alkene having a double bond between the carbon atoms. Writing C1H2 will simply change the whole structure and moreover the Carbon atom will not be able to complete its octet.(5 votes)
- [Voiceover] We've now seen a couple of examples of balancing chemical equations. And we've seen that, okay, if let's say, we're trying to balance this equation right over here and we started with the carbons. I have two carbons on the reactant side. They're both sitting in this ethylene molecule. And so I would want two carbons on the product side. And right now, I only have one carbon on the product side. And so what we've done is let's just put a two out front here and so now we have two for every molecule of ethylene and we're not done balancing this chemical equation yet. We're now producing two molecules of carbon dioxide. But one thing that you might have been thinking, "Why put this big two out front "of the entire carbon dioxide, "I like the way these little subscript little twos look, "so why not put a two right over there. " And the reason why you can't do that is that's actually changing the molecule. It's no longer carbon dioxide, it's now this bizarre thing that doesn't really exist in nature. Which is a C2O2 thing. You're actually changing the reaction when you're doing that. When you're balancing chemical reactions, the reaction itself is, even before it's balanced is describing something that happens. When it's unbalanced, it just doesn't have the numbers right in terms of number of molecules. So the only thing that you can change when you're changing these is the number of molecules. You can't change the number of constituents within the molecule. And that's why we do not change these subscripts. And if you want to visualize it a little bit differently, let's draw each of these molecules So ethylene looks like this. Double bond carbons. Then each carbon is bonded to two hydrogens. Notice you have two carbons and four hydrogens. Molecular oxygen, O2. Looks like this. It's oxygen doubled bonded to oxygen. And then you have carbon dioxide. Carbon dioxide is a carbon, double bonded, to two oxygens each. And then finally, you have water. Finally, water, actually I'm going to do this in a slightly different color. Your water right over here, this is an oxygen bonded to two hydrogens. So let me write the plus signs there. So plus is right over there. So if you were to somehow write a subscript of two right over there, you would somehow be changing the structure, you would be changing what this molecule is. As opposed to that, which we don't want to do, we want to say, we're definitely producing carbon dioxide. We're definitely producing carbon dioxide, but how many carbon dioxides do we produce for each molecule of ethylene? And so that's where we say, "Okay, we have two carbons here, "we want two carbons here." We don't want to change the actual structure here, so let's write the two out front. So we're going to have two of these. Or if you want to do it, if you want to have it more visual, you could write it, okay, we're just going to have another molecule here. We're just going to have another molecule. So now we've balanced the carbons, two carbons on the reactant side. Two carbons on the product side. And then you go to the hydrogens. Say, "okay, we have four hydrogens here, "we only have two here." Well, what if we had two of these water molecules? So, let's draw another water molecule here. So O H, and actually let me write this right over here, so now we have two of these. And now we have two of these. And now we want to balance the oxygens. So let's see, on this side we only have two oxygens. On this side we have one, two, three, four, five, six oxygens. In order to balance it, we're going to have six oxygens on the reactant side. We need three of these molecules. So, another one and another one right over there. And now we're all balanced. We have two carbon atoms on both sides. Carbons, carbons. We have four hydrogen atoms on both sides. Here they're in the ethylene, here they're in the waters. And then we have six oxygen atoms on both sides. And here some of the oxygens are in the carbon dioxides, some of them are in the waters. And here, they're all in the molecular oxygens. But notice, we didn't change the actual structure of the molecules. We just changed the number of molecules we have and that's what these coefficients in front of these molecular formulas represent.