2019 SCIENCE 5124 PAPER 2 ECZ SECTION A

let's get down to business okay question one reads which of the following is an example of the application of chemistry in the home now this question is specific so you have to be taking note of the key words okay so the key word here that is this one application of chemistry in a home now chemistry is applicable in almost everything that we do in life but this particular situation they want the application of chemistry in your home so basically we want to look at the thing that we do in a home and which ones are chemistry so basically anything that involves reactions anything that involves chemical like is from the home ok let's look at the choices that we have a we have the use of amplifiers in radio B we have the use of cosmetics C we have production of ammonia in the hubba process and option D we have industrial production oh oh now let's start from D D cannot be the answer because even in the beginning we are safe industrial production so this one is an industrial industrial application let's go to C now production of ammonia in the Haber process that is also an industrial production where ammonia is produced in the large quantities salt that one is out now let's look at the use of cosmetics so the use of cosmetics we are talking about things like lotions soaps and so on and so forth things that we tend to using the things for our body lotion for our bodies chemicals for the hair and other chemicals so those go for under cosmetics so definitely we was the correct answer here now why is a not the correct answer the use of amplifiers in the radio wow this is more physics and chemistry so the correct answer for a one is B let's go to question two the best operators that is used to accurately measure a required fixed on the reagent during titration is now let's look at the choices that we have so choice a this is a measuring some sort of a beaker okay so this one it does not give specific volumes okay then B this is a pipette as you can see most of it fits there even written to a transit meter cubic meaning this one can only measure 25 centimeter cubic so this is accurately the required volume so whenever you will need to measure an exact amount of volume during at Electrician we use what we call a pivot so B is a pivot then C this is just another type of the measuring cylinder then till this one is a burette so impurity is used when titrating that is where we put mostly the solution mousse concentration is known so the best answer also in here is B for my explanation P is a bit better and a pipette is mostly used when you are trying to measure an exact volume during a titration okay we proceed question 3 the question reads the best method to separate a mixture of sand and diesel is now let's look at the choices so choice a is taken tension now in order for us to choose we need to be understanding what each of these option means so the contention is simply a method that is used to separate liquids and solids in a scenario where a liquid can be pulled out leaving the solid into a containing vessel for example a stone and water we can gently pull out the water leaving the stone in today container so that is an example scenario where we use decantation so meaning sand cannot wait because we are pouring sand can also come out together without the desert okay then distillation this one is a general process which can be categorized into two we have what we call fractional distillation and we have what we call simple distillation so fractional distillation is used to separate miscible liquids than up with different boiling points for example water and even then simple distillation is used to a simple distillation is used to separate substances that can vaporize and be condensed back into a liquid okay let's look at C so C is evaporation so usually this one is used to separate water from a solution okay for example a salt solution we can remove the water layer leaving the SWAT crystals or they are cone or even a sugar solution let's look at filtration so filtration this is the one which usually we can use to separate a mixture of liquid and smaller solids for example the sand they deserve isn't biblical and the Sun is in certain point so the Sun is going to be trapped on the fuel filter paper and it will be called the residues then the diesel who passed through as a filtrate which will be collected in a beaker or any receiving vessel okay so the best answer that we had for question three is D okay let's proceed to question for question 4 is identify an inert gas from the diagram below okay so diagram a this one as you can see it represents what we call a diatomic gas because there are two atoms this is an atom and that is an item so this one represents a diatomic gas then P this one represents what we are calling a mixture so B represents what we are calling a mixture because you can see there are two different types of atoms in here and we are not chemically combined so this is definitely a mixture then we look at this one this one is this specific it's a mono atomic gas okay it is specific it's mono atomic and there is no combination of anything else oh this one is a mono atomic gas then D this one is a compound because you can see the two atoms actually chemically combined okay so now the question reads identify an inert gas so an inert gas is definitely C because this one is the only one which shows a mono atomic gas okay we can proceed to question five the following equation is incomplete now they are same two lithium hydroxide plus sulfuric acid is equals to X now here we need to have our basic knowledge we need to have our basic knowledge which says when you add an acid so when you add an acid so I'm just trying to summarize an equation here an acid plus a base so this bu before the best it is going to give us what we call a sort okay sort so we're going to have a salt plus water so a salt plus water so this one is water that is the general equation for the reaction between so now we are saying every time lithium hydroxide or hydroxide a basis there how come is to be specific then this h2so4 is an acid so acid plus base will give us a salt and water so now how do we know we get the metal patch here the metal part of the best plus the last part of a acid they tend to combine together that is what holds a salt then the remaining patch here the whole edge and the h2 is what is going to give us the water so if we get the medium and the South it there so we discover to say this is err area and lithium has got a balance of 1 then the South hso4 this definitely has a balance of 2 so when we swap is 2 here we are going to find Oh Mira li-2 yes oh oh so this is the name of the sort that we are going to form then this one will be plus the water which is h2o so this is what we expect so X we expect that it is going to be this one okay so let's check on the choices if we have anything that looks like this okay and also always remember to balance out the equation so since there is two lithium decide even this lithium is two there is two hydrogen this side then let's check also here meaning on water we are supposed to add it to so that the hydrogen's we have here is two plus the two here which is four so even here therefore then the oxygens here we have four oxygen plus this oxygen that is there making it six even on the product side here we are also having two oxygen plus 4 which is 6 so this is the rest so let's check an option a is Li to s Co 4 plus 2 so this one is definitely our answer according to our analysis ok so we can proceed I think there is no any other answer here so we can proceed we go to question 6 which reads which of the following molecules has a triple bonds which of the following molecules has a triple bonds now chlorine two chlorines that is two chlorines they are simply going to do something like CL CL and then this one it lacks one so they are going to share just 1 so it is going to just be like that because when a 1 dash represents a bond this one represents a bond which represents two electrons so only two electrons are shared here okay so we have analyzed a doesn't have a triple bond let's go to B which is carbon dioxide so we are going to have a carbon here then and and an oxygen there so meaning oxygen this one carbon here has got a balance of form meaning it requires four more so it is going to share it is going to share for this site so it is going to have two and four electrons even decide to be two and four electrons why because one bond represents two electrons so this is 2 4 2 4 so that when you add this 4 plus this form this one becomes a bow with 8 then oxygen also is sharing in form Plus this other two that is they're making it eight so this one is stable so having tested this one we know that it can't be the answer now nitrogen is one weird guy so nitrogen this one is possible that it can have a triple bond so it is going to be like this and then if you have something like this so it's gonna be two four six then plus the two here and two so it is going to have something right right okay so something like that even here it has something like this so when you check it is now balanced so nitrogen is definitely our answer which is C let's check out my equation below question 7 the question reads the diagram below shows the preparation of sorts the diagram below shows the preparation of a sorts so here let's look at the sorts that we have so we have silver nitrate reactant sodium chloride so these are both in awkward so these are two soluble salts that are reacting to produce an insoluble salt and a soluble salt so this type of a reaction is what we call a double decomposition so this one would be called a double composition so the double composition is a type of reaction in which two soluble salts are used to prepare an insoluble salt and in the process one a one or one of the swords produced is so soluble okay so now how does it happen so these two sorts are their reactive they tend to exchange their last pots so these last parts will be exchanged so this was a silver nitrate when you go decided to be super tall because the chlorine will cross over then the nitrate will close oh I will cross over to there which becomes sodium nitrate so definitely this one is called a double decomposition or a precipitation reaction okay having analyzed that let's check what our question says it says which of the following gives the correct description of the equation so for the sorts the given as silver chloride and they're telling us that this is unreasonable salt which is true then the method of separation here it's definitely filtration because we have a solid and we have so we have so we have a solid and we have a solution so we have a solution and the solid so filtration is not going to x-ray so let's go to this one sodium nitrate yes it is a soluble salt now how can it be separated from this guy here okay we put that on question mark can we put it on question mark then we go to silver chloride so silver chloride is not soluble so definitely see and and T are not correct because silver chloride is soluble and sodium nitrate is e soluble so these two energy and Sons so let's check on on these two answers between a and B so now we know that these two so how do you separate an insoluble salt from a soluble salt I think the best thing here is filtration so I think the best answer that we'll go for here is e a okay so we proceed question eight the question reads what mass of copper to oxide would react completely with five hundred sand meters cubic of 0.5 mala dilute sulphuric acid okay so we are looking for mass here now looking at the kind of data that they've given us this one which we have been given here this one is there for you and this one that we have been given here it's the concentration so the only way out here is to use the formula which says concentration is equals to okay number of moles over volume this is the formula that is going to help us here now in order for us to use this dysphonia we have the concentration here and we have the volume here so now since we have this volume the testing we have to make sure that all the volumes they are supposed to be in decimeter cubic so in order to convert we are just going to divide this one by a thousand so this one divided by a thousand because 1000 centimeter cubed is equal to one day's Rita that's why we are dividing by a thousand so dividing that one by a thousand we are definitely going to have a concentration of about 0.5 so we're going to on our 0.5 this meter cubed so 0.5 this meter cubic okay that's what we have now using this one we are now going to just say okay in this case it implies that number of moles is equals to 0.5 which is concetration 0.5 decimeter cubic multiplying with the so the zero day there 0.5 decimeter cubic multiplying with a zero OMG five and we expect that our answer here number of moles of definitely this 0.25 moles so we have 0.25 moles then now from here we are going to use the formula which says number of moles is equal to mass over molar mass so mass over molar mass that is what you're going to use now we can easily find the monomers from this because they've said Copa to oxide so we can easily make a phony run for copper two oxides now Copa I'll put a balance of it so we do see you little balance of tune then oxygen also with a balance over two so when we swap these ones down here we are still going to have see you two here down then all we also have a two down here so because these can be cancelled out we cancel out we cancel out this means that our formula is going to be see you oh so now here we can easily add down so Copa has got about 64 grams per mole so we add plus the one for oxygen so oxygen is e 16 so now in chemistry you can even use a calculator so you can easily add 16 plus 64 so let's do that on the calculator so that is 64 plus 16 this one is going to give us 80 grams per mole so our answer here is 80 grams and one so 80 grams okay so now having found that we know that to find the mass here we are going to multiply the number of moles multiplied by the molar mass and the number of moles rope which to file so multiply this one by 0.25 so we multiplied by 0.25 and this one is going to give us an answer all about so let's do that on the calculator so we multiply the 80 grams per 1 kg multiplied by 0.25 and we have our 20 grams so our answer here is 20 and that is our final answer then we just have to counter check if we have such a thing on the answers and it corresponds with V D okay so let's go - lets go - lets go - question 9 question 9 reads question 9 reads the table below shows some transition elements and their uses which one is the correct use in the contact and the hubba process so now interesting that you need to know is that they have a process this is the industrial production of ammonia and ion is used as a catalyst okay so having having known this one we should also ask ourselves what is the conduct process now in the contact process the contact process it's also a process in the contact process is the current method of producing sulfuric acid so now they the one that is used here platinum was initially used as a catalyst for this reaction however it is subset susceptible to reacting with it as any impurities in the South a feedback so instead they use vanadium so we are saying here we use vanadium then in the hubba process we use ion so definitely it feels adjusted remembering questions so you have to know that the contact process this one is the industrial operation of securing acid and the catalyst that is used is the vanadium then other process is the industrial preparation of ammonia and the catalyst is easy iron okay then let's look at question 10 so which all the arrangements below is suitable for collecting a gas that tends are any air okay gasps that is denser than air so now advance that is denser than air it should be collected by what we call downward displacement of air so it should be collected by what we call downward displacement of air so I think in the next segment I'll talk more about question details for that I'll be able to explain what each of these 10z is supposed to mean okay so we leave this one hanging just a bit says something that I need to explain okay so question 11 this one it reads the relative formula mass or calcium hydrogen carbonate is now these are simple questions calcium hydrogen carbonate so here we just start dealing with it right here so carbon here we have got 3 times 2 which is 6 so we have got about 6 multiplied by the mass number of oxygen is 16 so there we can find that one and go to carbon as well so how many couples do we have we have only about 2 carbons so to multiply it by 12 okay we are also supposed to find the total there then we go to hydrogen so hydrogen here we only have 2 and hydrogen is e 1 so this is 2 multiplied by the mass number which is 1 then finally we have our cows on here which is also just 1 multiply it by 40 so 1 multiply it by 40 so let's just fill in the answers there and you can quickly do this with a calculator that is the beauty of chemistry so 16 times 6 pretty sure why this one is going to give us rest check them with a calculator 16 times 6 sit still multiply by 6 just 16 multiply by 6 that is 96 okay so here we are going to find that it is 96 grams per mole then this one 2 times 4 this one will give us 24 okay then this one is going to give us just 0 2 then this one give us 40 so what we do we now add the total for everything because we are finding relative molecular mass so we add 96 plus 24 plus 2 plus 14 and we have our 162 so 162 is our answer so let's check on the choices do we have 162 okay there our answer is d ok question through the question reads which of the following statements explains why magnesium calcium and barium are placed in group of the periodic table okay so now remember a periodic table is simply an arrangement in tabular arrangement of elements according to their increasing proton numbers ok so now this they were placed in groups and periods based on their physical and chemical properties okay now let's check out so group two elements they all have two electrons in the outermost shell which is true they form basic oxides that are soluble in water we can put that one on question like their outermost electrons are lost when they react with nonmetals ok which of the following statement explains why magnesium is placed in group 2 so the reason why it is placed in group 2 the other things might make sense but the reason is because the electro the valence electrons is two valence electrons is simply the number of electrons in the outermost shell this is why a is our best answer question 13 this one reads how many molecules are found in six point so six point zero deaths with a cubic of carbon dioxide are t-ara TP so now here we are going to say one more they are two thing that we can use here so how many molecules okay now we know that one more okay one more this one is equals to so one more is equals to the Avogadro's constant which is six point zero two other they made a decree multiplied by 10 to the power 23 molecules so just one more will give us that then we also know that one mole of any gas at RGB is also equivalent to 24 this meter cube so we are going to use these two packets here they are going to help us to do with what we have so we know that one more is a constituent for this Rita then also the same one mode is equal to six point zero to ten z24 to the power at the time a times 10 to the power 23 so what we can easily do is we can easily say okay here we have our 24 we equate it directly to the Avogadro constant which is six point zero point zero two times times 10 to the power 23 we equate it like this then now we are going to ask ourselves how about six decimeter cubed will be equal to one so this is just meter too big it's a volume let's make a cubic even this six also point zero it's also in decimeter cubed which will be equal to X so when we make our equation here we are supposed to cross multiply here so we can just go to the calculator and do that one so we are going to have 24 X being equal to so the six a six point the six point zero three so let me try just to do this one it's six points so six point zero 6.02 x and to the power 23 to the power 23 this is been multiplied by six okay so when you multiply this one by six we are going to actually divide it so we have something like three point six one three point six one three point six one two times ten to the power 24 then we divide this one by 24 okay so we have put something like 1.5 times 10 to the power 23 so x-max wacho calculator is properly set X to be equal to 1.5 times 10 to the power 23 so this is the number of particles then we are going to check we have 1.5 times 10 to the power 23 and we have our answer right there okay f-14 which of the following is an alloy now we just need to be over Rouen overruling these things rust is simply a brown substance that is formed when iron reacts with the oxygen in moisture conditions so it can be an anode then silver silver is definitely a pure metal okay tungsten is also a few a metal so our best here is bronze so bronze is definitely an alloy now an alloy is a mixture of two or two or more methods or even in rare cases some metals so the purpose of allowing mixing metals together is to improve their strength and other qualities okay f if teen the question reads so f-15 the question reads halogens are useful elements but also caused harm to the environment halogens are useful elements but also caused harm to the environment which of the following is danger of halogens so we're ooh this one is not true they don't cause HIV and AIDS they are used to treat wounds or release so it's one as much a dangerous thing to teens is not a dangerous thing so they already see um for injections no they don't release radiations the only danger points in form of the tetra chloro methane's or something that's when they tend to contribute to the depletion of the ozone layer so the best answer here is B of the following is not so we are emphasizing only not and that is how we can best find our answer okay we got to question Mangini the compound represented below is so you just check it out so good watch come on here and come on here so definitely you can make that is c2 then we got hydrogen here 1 2 3 4 so good h4 so definitely you can recognize this because it corresponds to the formulas general formula cnh2n H then e2 and then because it has got 2 so 2 min egg so meaning this is the general formula for our teens meaning this one is e 18 so this one is if in white because if I put it to there and the two there it will give me exactly this one so this one I know now it's only a thing of which it is e a so someone might be wondering why not even eaten Oh a thousand for each sandwich why not Ethan Ethan should have conformed to the general formula cnh2n plus 2 so unless if we had six at the end they need to dive in and detain so the best answer in this is is a okay what is the name of a compound below so the compound below we first of all have to identify this this point here okay so this point here it looks like a anyway what if I go this is an ester linkage this is an ester linkage so definitely if we know that this is an ester linkage we know that this whole compound is definitely an ester okay this one is definitely an ester now how do we name a stance how do we name a stance so instance you just go to the name of the acid so - the name of the acid you remove the oil facts and then add yl so you remove for example if you have in this case it was ethanoic so either it a noise like this either knowing acids okay then you just have to remove this one all of it you remove it here then you add Y L this is where the ether comes from then from the name of the alcohol so from the name of the alcohol you just have to remove the last patterns and OHT this is how come this one becomes it out internal it has the best answer so you just remove here all day only here because Ethan oh who always for example this one ethanol would be like this let's try to explain this one again so that people can me get it okay so now I said to an acid because it would be like it annoying so you just remove from here you just get a fist three letters the earth facts if a prefix so just get the prefix then to the prefix add white arrow then do the alcohol back because I'm ester is a compound formed when an alcohol a carboxylic acid reacts they join together with the expulsion of water quality that's why it is a condensation polymer so in water molecules we the acid and the elbow they combined together now when they combine together how do you come up with a name so from the acid but you have to just get the critics which is the prefix we know that the ten prefixes in organic chemistry so you just get the prefix then you from the prefix you add y el then to the eternal back there you just have to remove the air just remove the air and add a and c e now remember when you add this Plus this one we had that first it gives us the name ether internally therefore our answer is this one thank you so much for listening please subscribe to our Channel and we'll be solving a lot of questions you just want to contribute to your personal development and your success