Types of Chemical Reactions

oh my god there are so many reactions in chemistry how am I going to learn all these chemical reactions don't worry in this video we are going to visualize the chemical reactions in an interesting way using these simple blocks since there are so many reactions we are going to divide them into five important types I'm also going to show you how to predict the chemical reactions based on these types so you won't have to memorize all the reactions and as usual we'll finish off with our top three questions on this topic chemical reactions can be divided into these five important types in this video we're going to look at each of these types and their examples now if you're not sure how to write chemical equations and how to balance them then I would suggest you to watch that video before continuing here so friends are you ready let's go to our chemistry lab first let's start with combination reactions in combination reactions two or more substances combine to form one single substance let's visualize it with our blocks here let's say we have two substances A and B and they combine to form one product a b this is a combination reaction in combination reactions you have two or more reactants but only one product now let's look at some examples let's say this pink block here is hydrogen and this block is oxygen now when they combine we get water this is a word equation since it's written in words now let's write it as a chemical equation so we have H2 plus O2 giving us H2O note that the product is not a simple join of the formula of the reactants so it's not H2O2 it's H2O because the elements combine according to the valency now here the equation is unbalanced so let's go ahead and balance the equation another example is magnesium and oxygen combine to form magnesium oxide so we have mg plus O2 giving us MGO now let's balance the equation and we get 2 mg plus O2 gives us 2 MGO in these simple examples the reactants were elements and the product was a compound but the reactants can also be compounds let's take an example let's say we have carbon monoxide and oxygen carbon monoxide is a compound and oxygen is an element and when they combine together we get carbon dioxide now why don't you try predicting the next reaction hint it's a combination reaction if you combine sodium and chlorine what are you going to get here sodium and chlorine combine to form the compound sodium chloride but the correct formula is NaCl it's not a simple joining of n a and cl2 because the elements combined according to their valency and valency of sodium and chlorine is both one so we get the formula NaCl let's put combination reaction on our concept board the key point is only one product next let's look at decomposition reactions decomposition reactions are the opposite of combination reactions in decomposition one compound breaks down into two or more simpler substances so once again let's visualize it using our blocks here let's say we have a substance a b it decomposes or breaks down into two substances A and B this is a decomposition reaction in decomposition reactions you have two or more products but remember only one reactant now let's take a look at some examples let's say we have water here and when you pass electric current it breaks down into hydrogen and oxygen this is also known as electrolysis since electric current is used to decompose the compound remember this equation is exactly opposite of what we did in combination where hydrogen and oxygen combine to form water another example of decomposition is when you heat calcium carbonate it decomposes calcium carbonate decomposes to produce calcium oxide and carbon dioxide this is called thermal decomposition since heat causes the decomposition now let's try predicting the next reaction do you know what happens when silver chloride is exposed to sunlight that's right silver chloride decomposes into silver and chlorine do you know where this reaction is used or rather was used in black and white photography where the film or the photographic plate contained silver chloride and it decomposed when it was exposed to sunlight to give us the black and white image of course now in the digital world everything's digital and we are using SD cards now let's consider another example digestion of food so when you eat food what happens in the digestion process is it a combination reaction or a decomposition reaction what do you think that's right the correct answer is decomposition reaction our digestive system breaks down the complex food substances into simpler substances for example carbohydrates are broken into simpler sugars such as glucose proteins decompose to form amino acids so digestion is a decomposition reaction let's pin decomposition reaction on our concept board remember the key Point only one reactant next let's look at displacement reactions in displacement a more active element displaces or takes the place of a less active element in a compound these are also called single displacement reactions let's understand these with the help of our blocks here so let's say here we have element a and compound BC now a is more reactive than b so it's going to displace or push off B and combine with C so now B is alone here so we have AC plus b this is a displacement reaction as we saw here the more active element a is displacing the less active element B now how do we know which element is more reactive than the other in chemistry we have a reactivity series here's what it looks like for metals metals on the top are more reactive and as you move down the reactivity decreases for example if you look here sodium is more reactive than iron hydrogen is also in this list even though it's a non-metal because it's electropositive in nature and can be displaced by metals there is also a reactivity series for non-metals the halogens this is what the simple reactivity series for important halogens looks like fluorine is the most reactive and iodine is the least reactive now let's look at some examples of displacement reactions let's say we have zinc and hydrochloric acid here now since zinc is more reactive than hydrogen according to the reactivity series it can displace it so we get zinc chloride and hydrogen this is our displacement reaction another example is potassium iodide and chlorine this example involves non-metals chlorine is more reactive than iodine so chlorine can displace iodine from potassium iodide and we get potassium chloride and iodine so here we had displacement of non-metals now let's try predicting the next reaction what happens when an iron nail is placed in copper sulfate solution first let's write down the reactants so here we have iron and copper sulfate now we know that iron is more reactive than copper so iron is going to displace Copper from copper sulfate and what are we going to get here in the displacement reaction that's right copper and iron sulfate we can even predict the observations based on this reaction so we know that copper sulfate is blue in color and iron sulfate is green in color so the color of the solution is going to change from Blue to Green and since you have copper being deposited here you're going to see a reddish brown deposit on the iron nail what do you think will happen if a copper piece is placed in iron sulfate solution what are the products now that's right there's going to be no reaction because copper is below iron in the reactivity Series so copper cannot displace iron let's put displacement reaction on our concept board remember the key point a more active element is displacing a lesser active element previously we did displacement or single displacement reactions now let's take a look at double displacement reactions in a double displacement reaction two compounds react with each other and exchange their ions to form two new compounds so let's go ahead and try it with the blocks here let's say we have two compounds a b and c d now there is an exchange of ions and we get two new compounds c b and a D this is a double displacement reaction now you may be thinking do we need to use the reactivity series again for double displacement reactions the answer is no reactivity series is only used for single displacement reactions because if you look at double displacement we can't say that a is displacing C or C is displacing a it's simply a exchange of the ions so remember reactivity series is only used for single displacement reactions now let's take a look at some examples of double displacement let's say we have silver nitrate here and sodium chloride to analyze the reaction let me switch these blocks so that the reactants and products match first split the reactants into their ions so we have silver iron and nitrate ion and sodium ion and chloride ion now you can exchange the cations or the anions so let's exchange the cations here if we exchange the cations positive ions silver and sodium we get sodium nitrate and silver chloride so this is our double displacement remember exchange the cations or the anions don't exchange both the cations and anions otherwise you'll get back the original reactants another example is sodium hydroxide and hydrochloric acid again let's go ahead and exchange the cations we will get sodium chloride on the product side and when o h minus and H plus ions combine we get water do you know another name for this reaction the correct answer is neutralization because sodium hydroxide is neutralizing hydrochloric acid to produce water and salt now let's try predicting our next reaction what happens if we mix lead nitrate and potassium iodide first let's write down the formula of the reactants so we have pbno3 whole two and Ki next we are going to cut the reactants into their respective ions now let's exchange the lead and potassium ion so what are we going to get that's right we'll get potassium nitrate and lead iodide now lead iodide is insoluble in water so it forms a precipitate and this is also called a precipitation reaction and since it's yellow in color we are going to get a yellow precipitate here let's put double displacement reaction on our concept board the key Point here is exchange of ions now let's look at the fifth and final type of reaction redox reactions redox stands for reduction and oxidation in these reactions one substance is being reduced and the other is being oxidized first let's understand the meaning of these terms oxidation and reduction in simple terms oxidation means addition of oxygen and reduction means addition of hydrogen but there are other ways of defining oxidation and reduction so let's go ahead and make a table of oxidation versus reduction we just discussed the first difference oxidation is addition of oxygen and reduction is defined as addition of hydrogen oxidation can also be defined as removal of hydrogen and reduction is removal of oxygen now oxidation need not be only addition of oxygen we can expand the definition to addition of any non-metal or electronegative element similarly reduction can be addition of a metal or Electro positive element now we can Define oxidation as removal of a metal or Electro positive element and similarly reduction is removal of a non-metal or electronegative element oxidation can also be defined as loss of electrons and reduction is gain of electrons you can remember the last difference with the help of this simple mnemonic oil rig oil stands for oxidation is loss of electrons and rig stands for reduction is gain of electrons let's look at some examples of redox reactions let's say we have copper oxide and hydrogen here and when they react we get copper and water now if you look carefully this is a displacement reaction because hydrogen is displacing copper from the compound copper oxide now let's take a look from the redox point of view so if you look here copper oxide is losing oxygen and becoming copper so copper oxide is getting reduced here and hydrogen is gaining oxygen and becoming water so hydrogen is getting oxidized in this reaction and remember always the reactants get oxidized or reduced not the products in this reaction hydrogen is helping copper oxide to get reduced to Copper so hydrogen is the reducing agent and copper oxide is helping hydrogen get oxidized to water so copper oxide is acting as the oxidizing agent so remember the substance that gets oxidized is the reducing agent and the substance that gets reduced is the oxidizing agent now let's take a look at some more examples of redox reactions let's say here we have copper and oxygen and when they react we get copper oxide now who do you think is being oxidized and reduced here let's take a look so if you look at copper copper is changing to Copper oxide so oxygen is being added to Copper so copper is being oxidized here now what about oxygen since a metal is being added to it oxygen is being reduced so oxygen is our oxidizing agent and copper is the reducing agent in this redox reaction let's look at another example hydrogen sulfide and chlorine react to give hydrogen chloride and sulfur now who do you think is getting oxidized and reduced in this reaction remember the answer to this question is only the reactants not the products so let's take a look at the reactants so if we see hydrogen sulphide it's changing to sulfur since hydrogen sulphide is losing hydrogen so that's correct it's getting oxidized and if you look at chlorine hydrogen is being added to it and it's becoming hydrogen chloride so chlorine is being reduced here let's spin redox reaction on our concept board remember the key Point reduction and oxidation are both taking place I hope the five important types of reactions are crystal clear to you now so next time you see a chemical reaction I would encourage you to fit it into one of these types and that will help you predict the reaction so you won't have to memorize all the reactions and now are you ready for the top three questions on this topic try solving these questions and let me know your answers and doubts by putting it in the comments below I promise to reply to all your comments as soon as possible so I'm going to disappear and you pause the video here and give these questions a shot I hope you found this video helpful and you have a better feel of the different types of chemical reactions and do remember to like comment and share out this video and if you haven't subscribed to my YouTube channel already go hit the Subscribe button right now you can also follow my Facebook page and do check out my website manochaacademy.com thanks for watching

Channel: Manocha Academy

Views: 2,310,840

Keywords: types of chemical reactions, chemical reactions, reactions, combination, decomposition, displacement, double displacement, redox, types of chemical reactions class 10, types of chemical reactions class 9, chemical reactions types

Id: WWJQpuv9ElE

Length: 20min 52sec (1252 seconds)

Published: Tue Jan 15 2019