Chemical Reactions (4 of 11) Decomposition Reactions, An Explanation

Summary

In this video by Step by Step Science, decomposition reactions are explored where a single compound breaks down into simpler products. It begins with the explanation of decomposition through the example of water breaking into hydrogen and oxygen, highlighting the importance of diatomic gases. The video continues with examples including sodium carbonate, sugar, and hydrogen peroxide's colorful breakdowns, providing insight into the balancing of their chemical equations and intriguing demonstrations like the 'elephant toothpaste' experiment.

Highlights

• Decomposition reactions start with a single compound and result in simpler elements or compounds.🧪
• Water decomposes into hydrogen and oxygen gas in a reaction often carried out by electrolysis.💧⚡
• The iconic 'elephant toothpaste' experiment involves hydrogen peroxide and sodium iodide as a catalyst.🐘✨
• Sugar's decomposition into carbon and water is an exothermic reaction creating a dramatic visual change.⚫💨

Key Takeaways

• Decomposition reactions involve a single compound breaking down into simpler products.🧪
• The 'elephant toothpaste' experiment with hydrogen peroxide is a visually amusing example of decomposition.🐘🥳
• Balancing chemical equations is crucial in understanding the products of decomposition reactions.⚖️
• Diatomic gases like hydrogen and oxygen play a key role in products formed from decomposition.🌿

Overview

This engaging video on decomposition reactions starts by explaining how a single compound breaks down into two or more simpler products. Featuring a variety of chemical concoctions, it provides examples, starting with the decomposition of water into hydrogen and oxygen, showing the importance of understanding diatomic gases.

It advances with dichotomous examples like sodium carbonate turning into sodium oxide and carbon dioxide. The breakdown of sugar into carbon and water with the help of sulfuric acid showcases an exciting reaction. Each step carefully balances chemical equations, enhancing the educational experience.

A fun segment unravels 'elephant toothpaste,' where hydrogen peroxide decomposes into oxygen and water, catalyzed by sodium iodide. This segment is not only informative but also visually captivates as bubbles and steam take center stage, demonstrating science's chemical beauty.

Chapters

• 00:00 - 00:30: Introduction to Decomposition Reactions In this chapter, the focus is on decomposition reactions, a type of chemical reaction in which a single compound breaks down into two or more simpler products. The chapter explains how to identify a decomposition reaction by noting the presence of a single compound on the left (reactant) side of the chemical equation, which decomposes into simpler components on the right (product) side. This is illustrated with the general representation of a compound breaking down into components A and B.
• 00:30 - 01:30: Decomposition of Water In this chapter titled 'Decomposition of Water', the focus is on understanding decomposition reactions, specifically the decomposition of water (H2O) through electrolysis. The chapter discusses identifying the products of this reaction, which are hydrogen and oxygen, and balancing the resulting chemical equations. The primary goal is to determine the appropriate representation of these products, ensuring an accurate depiction of the chemical process.
• 01:30 - 02:30: Decomposition of Sodium Carbonate The chapter discusses the diatomic gases, which include bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, and fluorine, remembered by the acronym 'brinkle Hof'. These gases do not exist as elemental forms when isolated as they form diatomic molecules. A specific decomposition reaction is discussed, which involves the breakdown of water into its diatomic components: H2 (hydrogen gas) and O2 (oxygen gas). The importance of recognizing elements that naturally form diatomic molecules is emphasized.
• 02:30 - 04:30: Decomposition of Sugar The chapter 'Decomposition of Sugar' primarily discusses the importance of balancing chemical equations, highlighting an example with hydrogen and oxygen. The process demonstrated involves balancing a chemical equation by adding coefficients to ensure equal numbers of each type of atom on both sides of the equation. Additionally, the chapter introduces the decomposition of sodium carbonate into other compounds, hinting at the creation of sodium oxide among other products, with an emphasis on understanding the role of oxygen in this process.
• 04:30 - 09:00: Decomposition of Hydrogen Peroxide (Elephant Toothpaste) The chapter titled 'Decomposition of Hydrogen Peroxide (Elephant Toothpaste)' primarily discusses chemical reactions and balancing equations. It begins with a focus on neutralizing charges in chemical formulas, specifically the interaction of min-2 and sodium plus one, necessitating adjustments to achieve a neutral charge. It then transitions to discussing the decomposition process of sugar using sulfuric acid as a catalyst.
• 09:00 - 09:30: Conclusion The conclusion chapter explains the process of predicting products and balancing chemical equations, using the decomposition of sugar as an example. In the demonstration, plain sugar is used along with concentrated sulfuric acid as a catalyst. The narrator emphasizes the importance of caution when handling the corrosive 18 molar sulfuric acid.

Chemical Reactions (4 of 11) Decomposition Reactions, An Explanation Transcription

• 00:00 - 00:30 okay in today's video I'm going to be going over decomposition reactions and uh decomposition reaction is when a single compound breaks down into two or more simpler products and you can identify decomposition reaction by the fact that you have a single Compound on the left hand side on the reactant side of your chemical equation and the right hand side you're going to have that compound broken down into simpler components so these are the products a plus b and this is our Compound on the left hand side you see we have a single Compound on the left hand side of our chemical equation right
• 00:30 - 01:00 right so here we have some uh decomposition reactions that we're going to do or some compounds that we're going to decompose and let's go through and let's see if we can figure out what the products are going to be and then also balance those chemical equations so we have uh water H2O we're going to decompose that that's simp that's commonly done by electrolysis so we have we know we're going to have hydrogen and oxygen those are our two elements and it's going to be broken down into elements so we want to know is it just hydrogen and oxygen like that ho or is it something else so we want to
• 01:00 - 01:30 remember we have our diatomic gases and you can remember the diatomic gases using this term brinkle Hof we have bromine iodine nitrogen chlorine hydrogen and oxygen and Florine those are the diatomic acids so you can see we're going to have H2 plus O2 oxygen gas and hydrogen gas they don't exist as Elemental hydrogen Elemental oxygen all right so that's the uh decomposition reaction for water into hydrogen and oxygen we know we have our diatomic gas
• 01:30 - 02:00 and um let's see we have want we want to balance this we have two hydrogen and two oxygen so we're going to put um a two here that gives us four hydrogen and that means we're going to have to put a two here and I think that chemical equation is balanced just like that okay now we have uh sodium carbonate and sodium carbonate is going to decompose into two other compounds all right and we're going to have n o sodium oxide but we know that oxygen
• 02:00 - 02:30 is min-2 and sodium is plus one so we're now we're going have to put a a two right there for our subscript so that is has a neutral charge overall and then we're going to also have carbon dioxide CO2 and I believe two sodiums one carbon three oxygen I believe that it's balanced just like that okay now we're going to decompose sugar and we can decompose sugar using uh strong acid like sulfuric acid as a catalyst so um let's go through and I'm going to show you that decomposition reaction before
• 02:30 - 03:00 we go through and predict the products and balance that equation so let's go do that right now okay we're going to do decomposition of sugar this is just uh plain sugar I bought at the store I have about plain granulated sugar I have about 100 milliliters of sugar in my Beaker and then to that as my Catalyst I'm going to add concentrated sulfuric acid this is 18 molar sulfuric acid you want to be very careful it's very nasty so I have about 100 Ms of sugar
• 03:00 - 03:30 I have about 50 mL of concentrated sulfuric acid I'm going to add the two and I'm going to stir it you'll see pretty quickly it's going to start to change color get it all mixed up nicely and starting to react you can see
• 03:30 - 04:00 that's decomposition of sugar and the black stuff you see is carbon the steam you see is mostly water of course it's a little bit of sulfuric acid in there so you don't want to breathe it but sugar will decompose into carbon that's the black that you see and then most of the steam you see is water Cu uh sugar decomposed into carbon okay that's always a kind of a attention getter you get that white sugar being uh broken down being decomposed into carbon and and water the carbon is the black stuff
• 04:00 - 04:30 that comes out of the beaker like that and then there's water and there also it's kind of an exothermic reaction because it gets kind of hot it is an exothermal reaction gets hot and there's some steam that comes from that so let's go through and balance that uh let's see we know that we're going to have carbon we saw the carbon is just C and then we know the other product is going to be water so that's just H 20 we want to balance that we have 12 carbons over here and we're going to
• 04:30 - 05:00 have to put a 12 here and in water there's a 2:1 ratio of hydrogen oxygen over here we have a 2:1 ratio of hydrogen oxygen in our sugar so we know we're just going to put an 11 right there like that okay I think that is balanced just like that all right now the last one we're going to do is hydrogen peroxide we can decompose hydrogen peroxide and I'm going to show you this reaction too this is a good one this one is known as elephant toothpaste so let's go and do that decomposition reaction right now and then we'll come back now we're going to be doing the decomposition of hydrogen peroxide so I
• 05:00 - 05:30 have just here a plain glass cylinder I think this was a flower base at one point and to that I'm going to add about 80 mL of concentrated hydrogen peroxide I think it's 35% hydrogen peroxide all right now to that I'm going to be adding some food coloring the food coloring is just for effect you see I have here green food coloring mix that
• 05:30 - 06:00 up and then to that also I'm going to be adding some plain dishwashing soap this is just so we'll get some bubbles out of it the food coloring and the soap are not part of the reaction okay so I'm going to mix that up like that now we have hydrogen peroxide in here and eventually if we stand here and waited long enough all the hydrogen peroxide will decompose into water and oxygen gas but we want to make it look a little more interesting we want to
• 06:00 - 06:30 happen more quickly so we're going to use a catalyst and the Catalyst that we're going to use is sodium iodide so I have a solution here of sodium iodide and to the hydrogen peroxide I'm going to add the sodium iodide and the Catalyst does not partake in the reaction it's not part of the reaction but it is going to make the reaction happen more quickly it's going to lower the activation energy so let's add the Catalyst and give it a nice little Spin and see what happens so you can see here we're liberating all that oxygen from
• 06:30 - 07:00 the hydrogen peroxide the bubbles are simply from the soap the bubbles are filled with oxygen gas it's an exothermic reaction you see we got a little bit of steam here from the water that's also produced and the green food coloring just is for effect okay so that's the decomposition of hydrogen peroxide by Catalyst of sodium iodide and the product of that reaction
• 07:00 - 07:30 are oxygen and water okay that's always a a good attention getter I think the kids in class always like that you get all those bubbles from the soap and those bubbles are filled with oxygen gas so we know from that reaction we're going to produce water and also oxygen gas oxygen being one of our diatonic gases and you can see we have um two hydrogens over here and two hyrogen over
• 07:30 - 08:00 here but we have three um oxygen on the right and two on the left so we know we're going to have to put a two here that'll give us four oxygen but then that gives us four hydrogens so then we're going to put a two here and that'll give us four hydrogen four oxygen on the left and four hydrogens and four oxygen on the right okay so those are all uh decomposition reactions we can identify those because we know we have a single Compound on the left hand side of our chemical equation as the reactant and then we're going to break
• 08:00 - 08:30 that down into simpler products and we can do those can be either elements or compounds okay so thank you very much I hope that was helpful and we will see you next time