C4 - YEAR 11

Question 1

What is titration ?

Answer 1

-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 . )

Question 2

S1 of titration rqp
-Why use concial flask .

Answer 2

Use a pipette , to transfer 25cm cubed of sodium hydroxide solution into a concical flask .
-Conical flask reduces the risk of splashing .

Question 3

Why is is it mprotant you allow the liquid to DRAIN OUT , of the pipette , rather than blowing it out using the pipette filler .

Answer 3

-Blowng the liquid out , will you give an incorrext value .

Question 4

S2 of titration rqp

Answer 4

-Add solutions of indicaor , such as methyl orange , to the alkali in the conical flask .

Question 5

S3 of titration rqp

Answer 5

Place the conical flask on a whie tile , so we can see he colour change more clearly .

Question 6

S4 of titration rqp

Answer 6

Fill a biurette with sulfuric acid .

Question 7

S5 of titration rqp

Answer 7

Add acid to the alkali , until the solution is neutral .
-Weus need to add enoguh acid for this to happen .

Question 8

S6 of titration rqp

Answer 8

-Once we see a colour change , we now add the acid dop , by drop until the solution is netural .

Question 9

S7 of the titration rqp .

Answer 9

It is improtant to swril the solution , to mak sure the acid + alkali mix .

Question 10

S8 of titration rqp

Answer 10

-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 ,

Question 11

S9 of titration rqp

Answer 11

-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.

Question 12

S10 of titration rqp

Answer 12

-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 .

Question 13

do practice questions on titration .

Answer 13

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Question 14

How do we calculate percentage yield ?

Answer 14

Work out the mass first.

Question 15

What neeeds to occur for 100 % yield .

Answer 15

-ever single atom of the reactants must to react to produce the products .

Question 16

One reason why it is not always possible to achieve 100% yield in a chemical reaction .

Answer 16

-Some of the product may be left when it is sepearated fromt he reaction mixture .

Question 17

Second reason why it is not always possible to achieve 100% yield in a chemical reaction .

Answer 17

-Some of the reactants may react in different ways to the expected reaction so we do not get the products we expect.

Question 18

Third reason why it is not always possible to achieve 100% yield in a chemical reaction .

Answer 18

Teversible reaction may not go to completeion .

Question 19

Do the question on the shee t.

Answer 19

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Question 20

What is the equation for percentage yield .

Answer 20

mass of porduct actually made/maximum theoretical mass of product *150

Question 21

-We cannot chieve greater than 100% yield . It would mean we CREATED ATOMS IF WE DID THAT

Answer 21

…MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

Question 22

Look at atom ecnocmy sheet two equations at the top .

Answer 22

-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 .

Question 23

What is tom economy (AKA ATOM UTILISATION )

Answer 23

-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 .)

Question 24

ATOM ECONOMY EQUTION

Answer 24

Relative formula mass of desired products (from equation )/Su of relative formula masses of all reactions (from equation)*100

Question 25

Kye things to remember when doing ATOM ECONOMY QUESTIONS

Answer 25

-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 .

Question 26

Do question on atom economy

Answer 26

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Question 27

Reactions often porduce unwatned side -products . These represent a waste of money …

Answer 27

-So chemist try to find a use fro these procuts eg in other reactions , that way the money is not wasted .

Question 28

Gas volumes key acts

Answer 28

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 .

Question 29

Formula to work out the volume of gas .

Answer 29

Volume(dmcubed)=Number of moles24
or n =v24

Question 30

Do the examples below .

Answer 30

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DO mroe quesitiosn at free science elssons using gas volumes .