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Decomposition Reaction - Concept

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

A decomposition reaction is a reaction in which a single reactant produces multiple products. An example of a decomposition reaction is when water is broken down into hydrogen and oxygen. In essence, decomposition is the opposite of a synthesis reaction.

Alright, so one of the types of reactions that you'll see in class are decomposition reactions and decomposition reactions are exactly the way they sound. It's going from a single reactant going to several products. Like when you think of something decomposing like trash or your biodegradables or whatever it maybe you think of something you trash breaking down into it's elements and several different products, which is exactly what's happening. You have one reactant, that's your key this is going to be your clue that it's a decomposition reaction breaking down into several products. So here's your skeletal reaction notice it's one reactant key key key to your several products.

Okay so what we're doing is we're going to be breaking the bonds and breaking bonds requires a lot of energy. So what sometimes you'll need to make this go faster is you'll need something called a catalyst. And a catalyst is something that speeds up a reaction and actually lowers the activation energy so you don't have, doesn't require as much energy for this reaction to occur and it actually speeds up the reaction process. So catalyst are typically used in decomposition reactions. So here are some examples of what you might see in class, you have your single reactants breaking down, you can break down to elemental form from sodium nitrite to sodium and nitrogen. It can break down to 2 compounds dinitrogen oxide and water or it can even break down into elements or elements and water, it really depends on what your reactant is.

Alright so let's actually talk about this in a little more depth, this is hydrogen peroxide you probably have it in your medicine cabinet at home and what happens if you keep it too long this reaction will actually take place and it'll break down into water and oxygen gas. So you don't want to keep hydrogen peroxide too long or else it's going to lose its effectiveness essentially and you're not going to be able to use it anymore. So you're going to make sure that you actually replace this quite often because this reaction does take place now it does take a while to do this but it will do this. So sometimes to make the reaction speed up we talked about using a catalyst. Let's actually do this breaking down into water and oxygen gas.

Let's actually do that with a catalyst and see what happens. Okay so right here we're going to call this Elephant tooth paste and you'll see why, so we're going to have a very strong highly concentrated hydrogen peroxide into our graduated cylinder we're going to add some dish soap just for fun and some food coloring just to make it more fun. Okay and then we're going to add our catalyst, potassium iodide is going to speed up the reaction and notice it goes right away and the soap is actually getting the bubbles from oxygen gas and then you'll also get water at the bottom and so this is an example of a decomposition reaction just in for a fact that the soap is in there to make it more fun. And here's another, there's another good one. Alright so this is, yeah so decomposition reactions are one of the 5 that you'll see in class.