C4 - YEAR 11 Flashcards
What is titration ?
-Used to measure accuratley , what volumes of acid an alkali react together completely .
-It is ofn used to calcualte the concentration of an UNKNOWN SOLUTIOn by heating it witha s olution of a known concentration .
CONCORDNT VOLUMES - TWO VOLUMES WITHIN 0.1CM SQUARED (ignnore and nonconcordant volumes in your mean . )
S1 of titration rqp
-Why use concial flask .
Use a pipette , to transfer 25cm cubed of sodium hydroxide solution into a concical flask .
-Conical flask reduces the risk of splashing .
Why is is it mprotant you allow the liquid to DRAIN OUT , of the pipette , rather than blowing it out using the pipette filler .
-Blowng the liquid out , will you give an incorrext value .
S2 of titration rqp
-Add solutions of indicaor , such as methyl orange , to the alkali in the conical flask .
S3 of titration rqp
Place the conical flask on a whie tile , so we can see he colour change more clearly .
S4 of titration rqp
Fill a biurette with sulfuric acid .
S5 of titration rqp
Add acid to the alkali , until the solution is neutral .
-Weus need to add enoguh acid for this to happen .
S6 of titration rqp
-Once we see a colour change , we now add the acid dop , by drop until the solution is netural .
S7 of the titration rqp .
It is improtant to swril the solution , to mak sure the acid + alkali mix .
S8 of titration rqp
-We need to red the volume of acid ,a dded from the biurette .
IMPORTANT TO READ IT CORRECTY
-sO MAKE SURW , it is at eye level with the surfsce ofr the liquid .
-The surface of the liquid naturally cuvres ,
-Scientiss claal this MENISCUS .
-SO read tge yrette at tge BOTTON IF TGE NEBUSCYS ,
S9 of titration rqp
-We usually repeat thsi titration several times until we gget two readings wwithin cm cubed ,
-We then take a meanv alue of this for a final volume.
S10 of titration rqp
-So now we have the volume + the concenration of the alkali .
-+the volume of the acid , eeded to neturlaise the alkali , we can now use this o calculte their concentrations of the acid .
do practice questions on titration .
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How do we calculate percentage yield ?
Work out the mass first.
What neeeds to occur for 100 % yield .
-ever single atom of the reactants must to react to produce the products .
One reason why it is not always possible to achieve 100% yield in a chemical reaction .
-Some of the product may be left when it is sepearated fromt he reaction mixture .
Second reason why it is not always possible to achieve 100% yield in a chemical reaction .
-Some of the reactants may react in different ways to the expected reaction so we do not get the products we expect.
Third reason why it is not always possible to achieve 100% yield in a chemical reaction .
Teversible reaction may not go to completeion .
Do the question on the shee t.
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What is the equation for percentage yield .
mass of porduct actually made/maximum theoretical mass of product *150
-We cannot chieve greater than 100% yield . It would mean we CREATED ATOMS IF WE DID THAT
…MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
Look at atom ecnocmy sheet two equations at the top .
-Both reactions produce ethnol , but which one do ou choose .
-In the first one , every single atom of our starting materail ends up in the porducts meaning NO ATOMS in the end are WASTE PRODUCTS , emaning the reaction is very EFFICENT .
-In the secon one NABR , is the wast eproducts ( so some of the atoms we put into the reaction IS WASTED ) , so it isNOT AN EFFICENT REACTION .
What is tom economy (AKA ATOM UTILISATION )
-aTOM ECONOMY IS THE MEASUE FO THE MOUNT OF STARTING MATERIALS that end up as useful products .
-THE IMPORTNACE : —> by minimising the production of unwanted porducts we save money (economic advatage .)
-We can aslo increase sustainability by not wasting resources (environemntal advanatge .)
ATOM ECONOMY EQUTION
Relative formula mass of desired products (from equation )/Su of relative formula masses of all reactions (from equation)*100
Kye things to remember when doing ATOM ECONOMY QUESTIONS
-Big numbers count.
-You will see in the question what is the desired porduct .
-CANNOT have an atom economy of more than hundred perecetn as that woul dmean we are making atoms which is not possible .
Do question on atom economy
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Reactions often porduce unwatned side -products . These represent a waste of money …
-So chemist try to find a use fro these procuts eg in other reactions , that way the money is not wasted .
Gas volumes key acts
One mole of any gas occupies a volume of 2dmcubed . (At room temperature and pressure) .
-ROOM TEMPERATURE IS TWENTY DEGREES .
-Room Pressure = 1 atmosphere . TO USE THE FORMULA BELOW , room temperature and ROOM PRESSURE HHAVE TO BE CONDITIONS .
Formula to work out the volume of gas .
Volume(dmcubed)=Number of moles24
or n =v24
Do the examples below .
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DO mroe quesitiosn at free science elssons using gas volumes .
