in this video we're going to talk about predicting the products of chemical reactions so let's start with the basics if methane reacts with oxygen gas what will be the products of this reaction now if you can identify the type of reaction you're dealing with it's relatively easy to predict the products so whenever you have a hydrocarbon reacting with oxygen it's a combustion reaction if this reaction is carried out to completion if you have excess oxygen the products will always be carbon dioxide and water and then all we need to do is balance the equation so the number of carbon atoms are balanced on both sides we have one carbon atom on each side now we do have four hydrogens on the left two on the right so we got to put a two in front of water let's put a 1 in front of methane the last thing we need to do is balance the number of oxygen atoms we have 2 oxygen atoms from the co2 molecule and 2 from water so we have a total of four oxygen atoms on the right side so we need four on the left therefore we need to put a two in front of o2 and now the reaction is balanced so let's say if we have c2h5oh and if we react with oxygen gas this is another combustion reaction so the products will be the same co2 and water and you know how to balance it so i'll leave it up to you if you want to balance it or not now let's say if we react zinc with oxygen gas what product will form in this reaction now when you mix two elements together you're going to get a combination reaction they're going to combine and form a compound so in this case a compound between zinc and oxygen will have what chemical formula zinc has a positive two charge oxygen has a minus two charge whenever you have two ions combining and if they're if they have the same charge even though the sign is opposite they're going to combine in a one-to-one ratio so the product for this example is zinc oxide and if you wish to balance it all you need to do is put a two in front of zinc oxide and a two in front of zinc and now it's balanced so let's say if we want to react magnesium metal with nitrogen gas what product will form in this reaction so we're going to get a compound composed of magnesium and nitrogen or magnesium nitride magnesium has a positive 2 charge nitride has a minus three charge so when combining these two elements it's going to be mg3 and two and now all we need to do is just balance the chemical reaction so we just need a three in front of mg and one in front of everything else so for the sake of practice let's look at one more example so let's react sodium metal with elemental sulfur feel free to pause the video and predict the product that will form in this reaction so we're going to get a compound between sodium and sulfur or sodium sulfide sodium has a positive one charge sulfide has a minus two charge so this is going to be na2 s1 or simply nh2s now to balance it we need a 8 in front of na2s so we can have 8 sulfur atoms on both sides now notice that we have 16 sodium atoms on the right 8 times 2 is 16 so we need a 16 in front of any and so this is how you can balance synthesis or combination reactions and how to predict the products if you have an element reacting with another element now what's going to happen if you have calcium carbonate and you subject it to heat anytime you heat a metal carbonate a volatile component will escape that volatile component is carbon dioxide gas and it's going to leave behind a metal oxide in this case calcium oxide so if we had magnesium carbonate and we add heat to it co2 will leave producing magnesium oxide now the reverse is true as well if we were to take calcium oxide and react with carbon dioxide this will be a synthesis reaction but it's different from the other sensitive reactions because we're not mixing an element with an element we're combining two compounds and this will form calcium carbonate so typically the reverse of a synthesis reaction is a decomposition reaction so if you know the decomposition products then you know that these two combine will just produce this if the temperature is low now let's say if we have a metal hydroxide and we add heat to it what products will be produced in this reaction if you heat up a metal hydroxide it's going to cause water to evaporate once water is removed you're going to get the metal oxide so let's say if we have aluminum hydroxide and if we add a lot of heat water will leave leaving behind aluminum oxide now you can balance it if you want to but well let's go ahead and balance it let's put a 2 in front of aluminum hydroxide so now we have two aluminum atoms so we have 6 oxygen atoms in total so we need a 3 in front of h2o so anytime you heat a metal hydroxide it's going to produce water and the corresponding metal oxide now let's move on to single replacement reactions let's say if we react iron metal with copper ii chloride what products will be formed in this reaction so iron metal is a solid and we're mixing it with an aqueous solution of copper chloride in a single replacement reaction the metal fe will replace the other metal copper so fe is going to pair up with cl fe typically has a positive charge i mean the positive two charge chloride has a minus one charge so this is going to be fe1 cl2 so one of the products will be fecl2 copper is going to be displaced out of the solution as copper metal and so that's going to be the products of the single replacement reaction let's work on another example let's say if we have aluminum reacting with nickel two chloride go ahead and predict the products of this reaction so aluminum is going to pair up with chloride aluminum has a positive 3 charge chloride has a minus 1 charge so the chemical formula of the product will be al1 cl3 or simply ao cl3 and nickel is going to be displaced out of the solution as solid nickel metal typically the compound nickel chloride and aluminum chloride is still dissolved in the solution now what about the zinc metal reacting with hydrochloric acid try this one in this case zinc is still going to pair up with chlorine the same way as aluminum paired up with the nonmetal chlorine now let's write the formula between zinc and chlorine zinc has a positive two charge chloride has a minus one charge so it's going to be zn1 cl2 zinc is going to displace hydrogen out of the solution and so it's going to be elemental hydrogen which exists as a gas so whenever you have an active metal and you react it with an acid hydrogen gas will be produced now let's say if we have a non-metal like chlorine gas reacting with an aqueous solution of sodium bromide what's going to be the products of this reaction in this case chlorine the nonmetal is going to pair up with sodium a metal ion and chlorine is going to displace the other halogen bromine out of the solution so when chlorine pairs up with sodium it's going to be a one-to-one ratio it's going to be na1 cl1 or simply nacl and bromine is going to be displaced out of the solution as diatomic bromine which is a liquid at room temperature so this is going to be the reaction if you want to balance it just put a 2 in front of nabr and nacl so whenever you have like a halogen reacting with an aqueous solution typically the halogen will displace the other halogen out of the solution so let me give you another example of this type of problem so let's use bromine and sodium iodide bromine is going to pair up with sodium producing sodium bromide and it's going to displace iodide out of the solution and iodide is a solid i mean iodine as a pure element in the compound is ilo died but as a pure element it's iodine so as you can see the reaction is very similar to balance it's going to be the same so now you know how to predict the products of a single replacement reaction now let's move on to a double replacement reaction let's say if we have silver nitrate reacting with magnesium chloride and these are two aqueous solutions what will be the products of this double replacement reaction ag is going to pair up with co ag has a positive one charge cl has a minus one charge whenever the charges are the same if they have the same magnitude they're going to combine in a one-to-one ratio produce an agcl and then magnesium is going to pair up with nitrate magnesium has a positive two charge nitrate has a negative one charge so combined it's going to be mg1 and o32 whenever you have multiple polyatomic ions in a compound you need to enclose it using parentheses now it turns out that nitrate is always soluble so magnesium nitrate is still dissolved in the solution however silver chloride is insoluble so it doesn't stay dissolved in a solution it's a solid product whenever you mix two aqueous solutions and if you get a solid product this is not just called a double replacement reaction it's also called a precipitation reaction anytime you mix two aqueous solutions and if a solid comes out of it now let's look at another example what are the products and the reaction between aluminum chloride and sodium sulfate both of these are an aqueous solution so feel free to pause the video if you want to try this aluminum is going to pair up with sulfate aluminum has a positive 3 charge sulfate has a negative 2 charge so the chemical formula is going to be al2 so4 3. you just got to replace the charges with subscripts so that's going to be one of the products now to get the other product we're going to pair up sodium with chlorine and because they have the same charge they will combine in a one-to-one ratio nacl sodium chloride is soluble so it's still dissolved in a solution aluminum sulfate is also soluble if there's no change in phase if everything remains in the equal solution then technically there's no reaction in this problem if no solid precipitate forms or any other new phases appear in this reaction then it's no reaction now let's move on to another example let's react sulfuric acid aqueous sulfuric acid with aqueous potassium hydroxide go ahead and work on this problem so it's another double replacement reaction hydrogen is going to pair up with hydroxide whenever you pair up h plus and oh minus this will combine to form h2o so this is a strong acid strong base neutralization reaction which will always produce water and salt now we need to pair up the potassium with the sulfate ion so this is going to be k2 so4 times 1 or simply so4 all alkali metals in group 1 they dissolve in water they're very soluble so potassium sulfate is going to be an aqueous phase and water is a liquid so the fact that we have this change of phase there is a chemical reaction occurring here so typically when you mix two aqueous solutions and if you get liquid water chances are it's an acid-base neutralization reaction let's try one more example let's make sodium carbonate with hydrochloric acid sodium carbonate is going to be an aqueous phase and the same is true for hcl go ahead and predict the products of this reaction so first let's pair up n a and cl so that's just going to be sodium chloride and acl and then we're going to pair up hydrogen with carbonate so hydrogen has a plus one charge carbonate has a negative two charge so initially when you combine these two you're going to get carbonic acid however carbonic acid usually doesn't stay like that at normal atmospheric pressure it would stay in that form under high pressure but at normal atmospheric pressure carbonic acid typically decomposes back into water and carbon dioxide so therefore the products of this reaction are nacl h2o and carbon dioxide now nacl is in the aqueous phase water is a liquid and carbon dioxide is a gas this reaction is known as a gas evolution reaction you