in this video we're going to go over the different types of chemical reactions that you need to know in your chemistry class so we're going to go over combination reactions which are also known as synthesis reactions we're going to go over decomposition reactions combustion single replacement double replacement precipitation acidbase reactions gas Evolution reactions and Redux reactions so let's start with combination reactions in this reaction typically you have two smaller substances combining to form a larger substance a good example is a reaction between a metal and a nonmetal let's say if we combine magnesium metal and react it with nitrogen gas when a metal reacts with a non-metal it forms an ionic compound magnesium as an ion has a plus two charge nitrogen as an ion has a ne3 charge magnesium is an alkaline earth metal alkaline earth metals are found in group two of the periodic table and since they have two veence electrons they typically will form a plus two charge nitrogen which is in group 5 a elements in that column typically will form a minus 3 charge now using the crisscross method we can see what kind of product these two elements will form so it's going to be mg3 N2 so that's how you can determine the product form by a metal and a nonmetal so now all we need to do is balance the reaction the nitrogen atoms are balanced already we have two nitrogen atoms on both sides and so all we need to do to balance it is to put a three so whenever you're balancing a reaction what you need to do is modify the coefficients which are the number in front of these substances the only time you need to change the subscript is if you're writing the chemical formula like what we did here just earlier but when balancing the reaction don't adjust these subscripts adjust the coefficients so this is one example of a combination or a synthesis reaction by the way this particular combination / synthesis reaction is it a redo reaction what would you say the answer is yes a Redux reaction is a reaction that involves a transfer of electrons one substance is oxidized and the other substance is reduced metals they like to give away electrons nonmetals they like to acquire or receive electrons as a metal gives away an electron it's going to form a positive charge positively charged ions are known as cats nonmetals which like to receive electrons they will acquire a negative charge which are known as anions so which substance is oxidized and which substance is reduced the oxidation state of any Pure Element is zero and magnesium in magnesium nitride has an oxidation state of plus two because we use that charge to write the formula whenever the oxidation number goes up the substance is oxidized so magnesium was oxidized in this reaction it lost two electrons as it went from 0 to plus2 oxidation always involves a loss of electrons now nitrogen started with an oxidation state of zero because it's a Pure Element and it went to3 so the oxidation state went down or was reduced from 0 to3 so nitrogen was reduced reduction occurred for nitrogen since nitrogen gained electrons it was reduced now the substance that is oxidized is known as the reducing agent and the substance that is reduced is known as the oxidizing agent reducing agents like to give away electrons so active metals form very good reducing agents oxidizing agents likes to acquire electrons so the nonmetals that are very reactive form good oxidizing agents another way you can tell if a reaction is a Redux reaction here's the quick and simple method if you see a Pure Element on one side of the reaction and if you see that same element within a compound a reduxx reaction has occurred that's a quick and simple way to determine if a reaction is a Redux reaction consider the reaction between calcium metal and oxygen gas so we have a metal reacting with a nonmetal feel free to pause the video and predict the product that will form and balance the reaction and also determine the type of reaction that we have here so whenever a metal reacts with phenominal we said that an ionic compound will form and so we know it's a combination reaction or a synthesis reaction reaction calcium is an alkaline earth metal so it has a plus two charge oxygen is a calogen and it has a minus two charge so if we use the crisscross method it's going to be initially ca2 O2 but notice that the subscripts are both even which means that we can reduce it if you can reduce it you should in this case we can divide both numbers by two you want to get the lowest whole number ratio so it's ca11 which we can simply write as CAO whenever the charges are the same even though the signs will be different you can simply combine the two elements in a one to one ratio so this is the reaction and calcium oxide is the product that will form now we just need to balance the reaction since we have two oxygen atoms on the left side we we need to put a two in front of CAO and so this is going to have a two here now is this reaction a Redux reaction is this reaction a Redux reaction what would you say so just like the other reaction this one is notice that calcium is a Pure Element on the left side but it's within a compound on the right side whenever you see that you know to Redux reaction calcium changes from 0 to plus2 so because the oxidation number went up calcium was oxidized now oxygen went from 0 to -2 the oxidation number went down so oxygen was reduced therefore oxygen is the oxidizing agent and calcium is the reduce an agent now let's try another example between a metal and a non-metal reaction so let's say if aluminum is mixed with elemental bromine what products will form from this reaction so we have a metal and a non-metal reactant aluminum as an ion will have a plus three charge bromine on the other hand is a halogen that has seven veence electrons it's found in group 7A and since it only needs one more electron to complete its oxide bromine will only form a negative one charge now using the crisscross method we know the formula is going to be A1 BR R3 so we're just going to write it as Al br3 so that's how you can predict the product of a reaction between a metal and a nonmetal now how can we balance this particular reaction so notice that we have two bromine atoms on the left but three on the right what is the least common multiple of two and three the least common multiple of two and three is six because six is divisible by two and three so what we need to do is try to get six bromine atoms on both sides six ID 2 is 3 and 6 / 3 is 2 so now we have six bromine atoms on both sides but notice that we have two aluminum atoms on the right side so we got to put a two in front of Al so that's how we can balance this particular reaction and it's a reduxx reaction we see bromine as a Pure Element on the left and within a compound on the right so in this reaction aluminum is going to be the reducing agent it's an active metal to give away electrons and bromine is a non-metal that likes to receive electrons so bromine is the oxidizing agent consider this reaction what happens when you mix calcium oxide with water so this is going to be another combination reaction whenever you put a metal oxide in water you're going to get a metal hydroxide this turns into calcium hydroxide so this is another combination reaction it's in the form a plus b turns into a now this particular combination reaction is it a reduxx reaction notice that there's no pure elements on any side of the reaction we have a compound plus the compound produces another compound so this is not a Redux reaction calcium oxide is known as a basic and hydde the reason being is when you add water to a basic and hydde it turns into a base whenever you see a hydroxide ion it's a base so whenever you put a basic and hydr with water it always turns into a metal hydroxide so for example let's say if we add another metal oxide like magnesium oxide if you put that in water this is going to turn into magnesium hydroxide so the way this works is the oxide ion within magnesium oxide and calcium oxide it's a strong base and it reacts with water so the oxide ion grabs the hydrogen from water so these two will turn into hydroxide notice that the oxygen on the left it had four lone pairs so now it's going to have three lone pairs because it's going to use one lone pair to form the bond between itself and hydrogen now another hydroxide will form as this oxygen gains two electrons from this Bond and so that's going to turn into another hydroxide so these two hydroxide ions they're going to pair up with either calcium or magnesium and you could see that there's two hydroxides in each of these compounds so here's the net ionic equation so when oxide is put in water it generates two hydroxide ions so let's say if we have sodium oxide what's going to happen if we put it in water what do you think the product will be so anytime you mix a metal oxide with water you're going to get a metal hydroxide so in this case we know that sodium has a plus one charge and the oxide ion well the hydroxide ion has a minus one charge so notice that the charges are the same so to write the formula for sodium hydroxide it's simply NaOH these two they will combine in a one:1 ratio and to balance it all we need to do is put a two in front of NaOH and we're going to have two sodium atoms on both sides two two oxygen atoms and two hydrogen atoms so we see that metal oxides react with water to form bases now what about non-metal oxides let's say if we take a nonmetal oxide such as sulfur dioxide sulfur is a nonmetal it's found in the upper right corner of the periodic table metals are found on the left so if we take this non-metal oxide and mix it with water what's going to happen non-metal oxides produce acids metal oxides produce bases so non-metal oxides are known as acid and hydrides if you put these two together you're going to get sulfurous acid now this reaction is it a Redux reaction we know it's a combination reaction but is it Redux notice that we have no pure elements on any side of the reaction so this particular combination reaction is not a Redux reaction another example if you make CO2 in water this can produce carbonic acid now if you see a double arrow that means it's reversible carbonic acid can decompose back into water and CO2 so those are just some more examples of combination reactions now the reverse of a combination reaction is a decomposition reaction so decomposition reaction typically has the formula AB which breaks down into two small components a plus b so carbonic acid as we mentioned can decompose back into water and CO2 this is one example of a decomposition reaction another example is sulfuric acid if you heat sulfuric acid it can decompose into sulfur trioxide and water sulfur trioxide is a gas water is a liquid depending on the temperature now if you heat it above 100 water is going to be steam it's going to be in a gaseous form so the phase of water depends on the temperature but typically whenever you heat up a compound if that compound contains a volatile component that volatile component is going to leave as a gas in this case sulfur trioxide is the volatile component and the last example where carbonic acid broke down into water and CO2 gaseous CO2 was was the volatile component another example of a decomposition reaction is one that is associated with water if you take electricity and if you pass it through water it can decompose into hydrogen gas and oxygen gas now to make it work faster you may need to dissolve a solute like potassium hydroxide and then pass an electric current through it now this particular decomposition reaction is it a reduxx reaction now this one is because notice that the water it breaks down into hydrogen and oxygen hydrogen is a Pure Element water is a compound so whenever you see a Pure Element on one side and a compound on the other side it's a redox reaction now which element is oxidized and which one is reduced the elements that are oxidized and reduced are typically on the left side of the reaction which is the reactant side I've never seen it on a product side or the right side oxygen usually has a -2 charge within a compound and as a Pure Element on the right it's zero hydrogen when bonded to a nonmetal typically has a plus one charge on the right side as a Pure Element is zero so notice that hydrogen it went from one to zero the oxidation number went down therefore hydrogen was reduced that means hydrogen gains electrons oxygen on the other hand it was oxidized the oxidation number went up it increased from -2 to0 so oxygen was oxidized in this particular example so since hydrogen was reduced in this particular example is considered the oxidizing agent and oxygen which was oxidized is the reducing agent now to make this reaction occur you need to put energy into it because oxygen is usually the oxidizing agent but this is a non-spontaneous reaction and we're put in energy to make it work without electricity this reaction would not happen if he makes hyd and oxygen they will naturally form water but this is one example of a decomposition reaction now let's say if you have mercury oxide which is a solid if you add heat what's going to happen whenever you see a triangle it represents heat if you have an ionic compound if you heat it high enough it can break down into its elements particularly if you have a nonactive metal within a compound the easier it is to break down into its components Mercury is a a non-reactive metal so when you add Heat this is going to produce Mercury metal and oxygen gas it's just going to break down into its pure elements Mercury is a liquid metal and oxygen is a gas so oxygen is the volatile component that leaves this particular compound now this reaction is a reduxx reaction we have a compound on the left and a Pure Element on the right now how can we balance this reaction to balance it we got to put a two in front of mercury oxide and a two in front of mercury and then it's balance now what's going to happen if we add heat to a metal carbonate when you add heat to it a volatile gas is going to leave the compound that volatile gas is carbon dioxide so once carbon dioxide leaves calcium oxide will be left over so for example if you add Heat to magnesium carbonate it's going to break down into CO2 gas and magnesium oxide now what about sodium carbonate what's going to happen if you add heat to it feel free to predict the products for this reaction so we know that we're going to get Co2 as a product and we're going to get a metal oxide sodium has a plus one charge and oxide has a minus two charge so using the crisscross method we can see that the compound that's going to be left over is na 21 so that's the formula for sodium oxide and notice that it's already balanced so we don't have to modify the equation now what's going to happen if we add heat to a metal hydroxide adding heat to a metal hydroxide will cause the removal of water so water is going to leave as Steam so to take out water from a hydroxide you need to add a a lot of heat and what's going to be left over is the metal oxide so let's say if we have lithium hydroxide if we add heat to it water is going to be removed and what remains will be lithium oxide lithium has a plus one charge oxygen has a minus two charge so using the crisscross methods Li 21 so anytime you need to write the formula of an ionic compound make sure you balance the charges when writing the subscripts so now let's balance this reaction by modifying the coefficients so we have two lithium atoms on the right side so we got to put a two in front of lioh and now the reaction is balanced so these are just some examples of decomposition reactions now the next reaction that we need to go over is the combustion reaction so let's say if we have an alkane such as methane methane is an alkane that contains one carbon what's going to happen if we react it with oxygen gas whenever you react a hydrocarbon with oxygen it's going to produce CO2 and water this is always going to happen so this is a good example of a combustion reaction a reaction where something reacts with oxygen it releases a lot of energy and it produces uh these compounds but now how can we balance this particular combustion reaction to balance it balance the carbon atoms first so we have one carbon atom on each side after that balance the hydrogen atoms so notice we have four hydrogen atoms on the left two on the right so we need to put a two in front of H2O and then balance the oxygen atoms we have two oxygen atoms in CO2 and 2 * 1 is 2 so we have two oxygen atoms and the two water molecules so we have a total of four oxygen atoms four / two is two and so that's what we need to do to balance it so the ratio is 1 2 one two now combustion reactions are they redox reactions the answer is yes a combustion reaction will always be a Redux reaction because you're going to have oxygen as a Pure Element and on the right side you can see oxygen within a compound so Redux reactions or I mean combustion reactions are redox reactions consider this combustion reaction ethane which has two carbons reacts with oxy oxygen gas to produce CO2 and water so go ahead and balance the reaction so let's start with the carbon atoms we have two carbon atoms on the left so we need to put a two in front of CO2 we have six hydrogen atoms on the left so 6 ID two is three so we got to put a three in front of H2O now notice that we have four oxygen atoms from the two CO2 molecules and 3 * 1 is three so three oxygen atoms from the three H2O molecules so we have a total of seven oxygen atoms 7 / 2 is 7 over 2 so right now we have a fraction which we don't want so to balance this reaction with whole numbers we need to multiply everything by two so let's start by putting a two here so now we have four carbons on the left side so we need a four in front of CO2 and we have a total of 12 hydrogens on the left 12 / by two is six so we need a six in front of H2O so now we have 8 oxygen atoms from the four CO2 molecules and six h i mean six oxygen atoms from the six water molecules if you add them you get 14 14 divided two is seven and so now the reaction is balanced with whole number coefficients so if you get to a point where you have an odd number of oxygen atoms on the right side you may have to double uh the entire reaction so you can start by putting a two in front of the hydrocarbon and then balance everything now let's do one more example on combustion reactions c2h5 is known as ethanol go ahead and balance this reaction feel free to pause the video as you work through this example so notice that we have two carbon atoms on the left so we got to put a two in front of CO2 and we have a total of six hydrogen atoms on the left 6 / 3 is 2 I mean 6id two is three so we need to put a three in front of water so we have six hydrogen atoms on both sides so in the two CO2 molecules we have four oxygen atoms and here we have three 4 + 3 is 7 now notice that we have an oxygen already in ethanol so 1 plus what number is s 1 + 6 is 7 so we need six oxygen atoms from the o2 molecules 6 / 2 is three so now the reaction is Balan we have two carbon atoms on both sides six hydrogen atoms and seven oxygen atoms on both sides consider this reaction aluminum is placed in a solution of copper chloride what's going to happen whenever you have a Pure Element mixed with a compound this is going to be a single replacement reaction now a is either going to displ B or C it really depends on a reaction but let's say a displaces b that means a is going to pair up with c and b is going to be by itself so whenever you have a Pure Element reacting with a compound it's a single replacement reaction single replacement reactions are Redux reactions but before we go into that let's predict the product of this reaction so here we have a metal reacting with an ionic compound the metal is going to displace the other metal out of the solution so aluminum is going to displace copper out of the solution and in the process of doing so aluminum is going to pair up with chlorine aluminum has a plus three charge and chlorine as an ion has a negative one charge so using the crisscross method the ionic compound that will form on the right side is going to be al1 CL three and then copper is going to be displace out of the solution as copper metal now not all single replacement reactions work some work others do not so you need something called the activity series which tells you the relative strength of metals in this uh type of reaction aluminum is more active than zinc zinc is more more active than Fe which is more active than hydrogen which is more active than copper which is more active than silver because aluminum is above copper aluminum metal is strong enough to displace the copper ion out of the solution so what's really happening is that aluminum metal is giving away electrons the copper plus two ion receives those electrons and turn into copper metal so the more active metal displaces the less active metal out of the solution so this reaction will work so now let's balance the equation notice that we have three chlorine atoms on the right two on the left the LCM of two and three is six so we need to put a three in front of copper chloride and a two in front of al3 so we have six chlorine atoms on both sides now that we have three copper atoms we got to put a three in front of Cu and a two in front of Al so now the reaction is balanced so we could see why this is a Redux reaction notice that we have aluminum as a Pure Element on the left side but it's in a compound on the right side so you can easily see why it's a reduxx reaction now the oxidation state of aluminum is 0 and in this compound it's plus three so aluminum went from 0 to 3 was it oxidized or was it reduced whenever the oxidation number goes up the substance is oxidized now copper on the other hand it went from the plus two state to the zero State you can tell that copper is in a plus two State because it has two chloride ions if there's one copper atom for every two chloride ions that means copper has to have a plus two charge it has to neutralize these two negative charges which adds up to -2 the overall charge must be zero for an ionic compound so because copper went down from two to zero we could say it was reduced and the substance that is oxidized is the reducing agent and the sub since that is reduced is the oxidizing agent so aluminum metal is the reducing agent in this example now what are the phases of every substance in this reaction the metals are in the solid phase the compounds are typically in the aquous phase for the compound sometimes it could be in a solid phase if it's insoluble in water if it's soluble if it dissolves in water then it's set to be in the aquous phase to figure this out you can use the solubility rules chlorides are generally soluble except with silver lead and Mercury since we don't have silver lead or Mercury copper chloride and aluminum chloride are soluble now how can we take this reaction and write the net ionic equation to do that everything that is in the aquous phase you want to separate it into ions so aluminum is not in the aquous phase so we're going to leave it the way it is copper chloride we need to separate it into ions so we have three copper ions and we have 3 * 2 or six chloride ions and on the right side we have two aluminum cations and six chloride ions two and three is six and then we have copper metal now this is the total ionic equation to write the net ionic equation eliminate the Spector ions the Spector ions are the ions that are found on both sides of the reaction so this includes the chloride ion so then what's left over is the net ionic equation which is 2 Al plus 3 cuu + 2 which turns into 2 Al + 3 and 3 cuu so this is the net ionic equation so copper and aluminum are in the solid phase the ions are in the aquous phase let's try this one iron metal reacts with zinc sufate will this reaction work so if you go to Google images and look up the activity series you'll see that aluminum is above zinc and zinc is above Fe which is above hydrogen notice that Fe is below zinc so that means that iron metal is not strong enough to displace zinc out of the solution so therefore there's no reaction for this particular single replacement reaction now what about the reaction between zinc metal and hydrochloric acid will this reaction work so zinc is above hydrogen on the activity Series so zinc is strong enough to displace hydrogen out of the solution so this reaction will work now what's going to happen zinc is going to displace hydrogen out and it's going to pair up with chlorine whenever you put a metal with an acid the metal is going to react with the acid if it's strong enough it can displace the acid out of the solution and produce hydrogen gas so zinc is going to form an ionic compound with chlorine typically zinc has a plus two charge and that's something you just got to know chloride has a minus one charge you can tell from the periodic table so it's going to be zn1 cl2 so we're going to get zinc chloride and hydrogen gas hydrogen in its Elemental form is diatomic so it exists as H2 so now we got a balanced reaction so since we have two chlorine atoms on the right side we need to put a two in front of HCL and now the reaction is balanced so we could see why this particular single replacement reaction is a reduxx reaction zinc is a pure metal and we can see that on the right side it's a compound so which substance is oxidized and which one is reduced so zinc went from0 to plus two which means that zinc was oxidized hydrogen went from plus one to zero as a Pure Element the oxidation state is always zero so hydrogen was reduced so since zinc was oxidized since it gave away electrons zinc is the reducing agent hydrogen received the electron so hydrogen is the oxidizing agent in both cases chloride is in the minus1 oxidation state so chloride doesn't participate in this reaction now how can we write the net ionic equation for this reaction zinc is in a solid phase hydrogen is in a gaseous phase and HCL is aquous and zinc chloride is Aquis so feel free to pause the video and write the net ionic equation for this example so the first thing we need to do is write the ions for everything that's in the aquous phase so HCL we can break it into H+ and cl minus on the right side the only thing that we can break up is zinc chloride in that compound zinc is going to be in a plus two oxidation state and we still have two chloride ions so you can see that the spectator ion are the chloride ions they appear to be the exactly the same on both sides of the reaction so now what remains is the net ionic equation so zinc reacts with hydrogen in a solution to produce hydrogen gas so you could see that zinc displaces the H+ ions out of the solution and so this is it this is the net ionic equation so don't forget to put the phases H2 is a gas zinc is a solid and the ions are in the aquous phase they're dissolve in water so let's go over one more single replacement reaction so what happens if you take bromine and you mix it with sodium iodide what's going to happen so bromine is a nonmetal it's a halogen a halogen is going to displace the other hogen out of the reaction so bromine is going to displace iodine out of the reaction and it's going to pair up with sodium sodium has a plus one charge bromide as an ion has a minus one charge because it's a one:1 ratio we can simply write it as NAB when iodine is displaced out of the solution it's going to be diatomic I2 so to balance the reaction all we need to do is put a two in front of nii and Na and so now it's balanced iodine is a solid bromine is a red liquid and the other two are in the aquous phase so we could see why this particular single replacement reaction is a reduxx reaction we have a Pure Element on the left and a compound on the right consider the reaction between silver nitrate and magnesium chloride so what products will form from this reaction so notice that we're mixing a compound with a compound this is typically a double replacement reaction which is in the form AB reacts with CD to produce now these two will get together and the two in the middle will combine so this is going to produce a d and CB so that's a a double replacement or a double displacement reaction so AG is going to pair up with cl AG has a plus one charge and cl has a minus one charge so the magnitude of the charge are the same so we can simply write the formula as agcl now what about the other two ions so what if we pair up nitrate with magnesium magnesium has has a plus two charge nitrate has a minus one charge by the way you should always write the positively charged cation first before you write the an so when these two ions combine they're going to produce a compound that's known as magnesium nitrate which has the formula mg32 whenever you have multiple polyatomic ions you need to enclose it within a parenthesis so that's how you can predict the products of a double replacement reaction so now we need to balance it so notice that we have two nitrates on the right side so we got to put a two in front of ag3 now we have two AG atoms on the left so we need a two in front of agcl and at this point the reaction is balanced now let's write the phases for the reaction which substance is in an aquous phase and which one is in a solid phase so for double replacement reactions you really need to know the solubility rules you can look it up on uh Google Images if you want to so the first thing you need to know is that nitrates are always soluble so if you see an NO3 it's going to be in an aquous phase chlorides are usually soluble except with silver lead and Mercury so we do have silver that's an exception so that's G to be a solid but magnesium is not an exception and chlorides are generally soluble so magnesium chloride is going to be in the aquous phase now whenever you mix two aquous solutions if you get a solid product this double replacement reaction is also known as a precipitation reaction silver chloride precipitated out of the solution silver chloride is a white solid now in this particular reaction is it a Redux reaction it turns out that double replacement reactions are never Redux reactions notice that we have no pure elements on any side of the reaction as we can see all we have are compounds so that's why double replacement reactions are not reduxx reactions there's no transfer of electrons now how can we write the net ionic equation for this reaction by the way if you don't get a solid on on the right side if this was an aquous substance if everything is aquous then no reaction has taken place unless you get a solid or a different type of phase other than Aquis that's the only time a reaction has taken place so to write the net ionic equation everything in the aquous phase we need to write it in terms of ions so let's break down this compound into its respective ions so we have two ag+ cat I and two nitrate ions and within magnesium chloride we have the mg2+ ion and two chloride ions on the right side agcl we're going to leave it the way it is since it's a solid and magnesium nitrate we can break it down into magnesium the mg2+ ion and two nitrate ions so what are The Spectator ions in this reaction so notice that we can cancel nitrate and we can cancel magnesium those are the spected ions now what remains is the net ionic equation but notice that the coefficient for what remains contains a two so if we divide everything by two the net iic equation is going to be ag+ which is in the aquous phase plus CL minus which is also in the aquous phase and this is going to produce solid silver chloride so that's the net ionic equation for this particular example now what about this reaction so furic acid reacts with sodium hydroxide this is another double replacement reaction but it's an acid base neutralization reaction we have a strong acid suric acid reacting with a strong base sodium hydroxide whenever you mix a strong acid and a strong base it's going to produce salt and water so let's find the products of this reaction so H is going to pair up with o whenever you mix an H+ ion with an O H minus ion these two will combine to form H2O now let's pair up sodium with sulfate so that we can get the other product sodium has a plus one charge sulfate is a polyatomic ion with a -2 charge so to write the formula it's going to be na2 so 4 now what are the phases for every substance in this reaction acids are usually soluble in water so we can write Aquis alkali metals like sodium lithium and potassium are soluble so anytime you see na it's going to be in aquous phase now water is a liquid so this is our acid base reaction now let's balance it so notice that we have two sodium atoms on the right side so we need to put a two in front of NaOH notice that you have two H+ ions two hydroxide ions that's going to generate two water molecules so if you put a two in front of H2O the reaction is balanced so now at this point let's go ahead and write the net ionic equation so suric acid which is Aquis we can rewrite it as two H+ ions and a sulfate ion sodium hydroxide is in the aquous phase so we can rewrite it as 2 na+ and two hydroxide ions on the right side we have two water molecules since it's not an aquous phase we're going to leave it the way it is and sodium sulfate we can write that as two na+ ions and one sulfate ion so the spected ions are sulfate and sodium out of what remains let's divide the coefficients by two therefore the net ionic equation is going to be H+ plus oh minus which produces water this is typically the net an equation for a strong acid strong base reaction it usually simplifies to that equation here's another example consider the reaction between HF and K HF is a weak acid Koh is a strong strong base predict the products of this reaction balance it and write the net ionic equation so this is a double replacement reaction whenever H pairs up with o it's going to produce water and then K is going to pair up with f k has a plus one charge F has a minus one charge since the charges are the same we can simply write them in a one:1 ratio and the reaction is already balanced now HF is an acid which is typically in the aquous phase potassium is an alkaline metal and alkaline metals like sodium lithium and potassium are always soluble in water now these are general rules so in a typical chemistry course if you see potassium or sodium it's safe to assume that it's soluble so water is the liquid in this example now here's what we have to be careful strong acids like HCL and h2so4 they ionize completely however weak acids like HF it doesn't ionize much so when you're writing the net ionic equation typically you won't separate HF into H+ and F minus you'll leave it the way it is because it doesn't ionize completely maybe less than 5 % ionizes but for the most part the majority of it remains as HF so for weak gases like HF don't break it up into ions when WR in the total ionic equation so HF is going to stay the same Koh that ionizes completely so we can write that as k+ and O minus on the right side we have liquid water and potassium fluoride ionizes completely so we can leave it as k+ and F minus so the spected ions the only one that we have is potassium so what remains is the net ionic equation which is HF plus o minus and that produces water and F minus so water is in the liquid phase and everything else is in the aquous phase so that's the net ionic reaction between a weak acid and a strong base now what if we mix ammonium chloride with potassium hydroxide so we can see that this is another double replacement reaction what do you think is going to happen like all double replacement reactions K is going to pair up with cl K has a plus one charge CL has a minus one charge so these two will combine in a one to one ratio ammonium nh4+ is going to pair up with hydroxide now when these two get together because they have the same charge even though the sign is opposite we could simply write them together in the one: one ratio as nh4 now you have to be careful with this reaction because ammonium hydroxide decomposes into NH3 and water now this is something you have to know one way you can see it is that nh4+ is really the combination of NH3 and H+ so when you add hydroxide to it H+ and O minus will get together to form water so if you draw the Le structure this is the nh4 plus ammonium ion looks like this and hydroxide which has three lone pairs is a strong base hydroxide is going to grab one of the hydrogens from ammonia and so you'll be left with an H3 and H2O so hydroxide simply grabs the hydrogen and turns into water and leaving behind NH3 now turns out that NH3 is a gas so what we're going to do is we're going to replace nh4 with NH3 and H2O so we can rewrite the reaction like this nh4cl plus K produces KCl plus NH3 plus H2O so those are the actual products in this reaction so this reaction is known as a gas Evolution reaction the reason being is we're mixed in two aquous solutions ammonium chloride and Koh ammonium is always soluble by the way it's part of these solubility rules if we're mixing two Aquis solution and if a gas is produced as a result it's a gas Evolution reaction now water is in a liquid phase and KCl is aquous since K is always soluble now from this reaction how can we write the net ionic equation so just like before everything in the aquous phase we're going to separate into ions so we have nh4+ C minus k+ and hydroxide and so that's going to produce k+ CL minus NH3 which is going to remain the same that's a gas and liquid water which is also going to stay the same so now let's eliminate the spected ions which are potassium and chloride so therefore the net ionic equation for this example is ammonium plus hydroxide produces NH3 and water which we've shown the mechanism already so this is the net ionic equation try this example sodium carbonate plus hydrochloric acid go ahead and predict the products of this reaction so this is a double replacement reaction initially so we know that sodium is going to pair up with chlorine sodium has a plus one charge chlorine has a minus one charge so these two will combine in a one: one ratio so now let's pair up carbonate with hydrogen hydrogen has a plus one charge carbonate is a polyatomic ion with -2 charge and so when you combine them it's going to be H2 CO3 now whenever you get H2 CO3 from a reaction especially when you mix a carbonate with an acid H2 CO3 is going to break down into water and CO2 we mentioned this already it's going to decompose into these two gases so what we can do is replace the intermediate H2 CO3 with water and CO2 water is a liquid but CO2 is a gas which makes this another gas Evolution reaction everything else is soluble anytime you see na it's going to be an aquous phas and acids are usually soluble so now go ahead and write the net ionic equation for this example so on the left side we have two sodium cats and in sodium carbonate we have one carbonate ion and in HCL we have let's not forget to balanced reaction let's put a two in front of HCL and a two in front of NAC and now the reaction is balanced so we have two H+ ions and two chloride ions by the way these gas Evolution reactions which comes from a double replacement reaction are not Redux reactions we don't have any pure elements on any side of of the reaction on the right side we have NaCl and two chloride ions and then we have water and CO2 so the Spectra ions are sodium and chloride so the net ionic equation for this example is 2 H+ reacts with carbonate to produce liquid water and gaseous CO2 so this is the overall net ionic equation now there are two other common gas Evolution reactions that you may encounter in your Chemistry course the first example is a sulfide if you react a sulfide with a strong acid the reaction will go to completion and it's going to to produce H2S now you need to know that H2S is a gas and so when you balance it it's going to look like this I'm not going to write the net ionic equation but I'm just going to tell you what to look for to know it's a gas Evolution reaction so if you get H2S as a product it's a gas Evolution reaction the other example is if you have a sulfite and if you react it with a strong acid which will take it to completion next they need to react it in a 1:2 ratio sulfite can acquire two hydrogens and when it does it turns to H2 SO3 now H2S SO3 it breaks down into water and SO2 now the2 part is a gas so you can replace H2S SO3 and you can write as your products water so SO2 and NAC so for this reaction to work you got to have a strong acid by the way if you mix sodium sulfite with a strong acid but in a one to1 ratio it may not go to completion instead you can get NAC and nahso3 which in this example this is not a gas Evolution reaction so if you react it in the 1:1 ratio these two will combine to form hso3 minus so we need a 2:1 ratio to take it to completion so if you react it with another set of hydrogen ions then this turns into H2S SO3 and h203 once you have it can break down into H2O and so SO2 and so SO2 is a gas so at this point we've covered the most common types of reactions that you'll see in chemistry so this is the end of the video I hope you found it to be educational and have a great day