SS 3 CHEMISTRY

   LESSON 13

11^th,August 2020.

Topic:  Preparation  and  collection of gases

   Good morning everyone ,hope your weekend was good. Today we will look at the above topic, before then ,make sure you check the corrections to previous lessons .God bless you.

     In the preparation of gasses, various method are employed and it depends on two major factors.

[i]Vapour  density of the gas.

[ii]Solubility of the gas in water.

Gases which  are lighter than air[less dense  air]are collected by upward  delivery of gas also known as

Downward displacement of air .Gases in this category are :Hydrogen[H] and ammonia[NH ₃].

On the other hand ,gases which are denser[heavier] than  air are collected by  downward delivery of gas[upward displacement of air].Examples are HCL,NO₂,CO₂,SO₂,C l₂,H₂S, SO₃.

However ,gases with vapour densites close to that of air[vapour density of air is 14.4],these gases can

Neither displace air upward nor  downward. Such gases are collected over water ,if their  solubilitiies   in

Water  are negligible,  that is slightly  soluble or  insoluble in water. Examples of gases in  this  category 

Are O₂,  N₂O, NO, CO, N₂ and PH₃.

1. List gases that can be collected by downward displacement of air.

   SS 3   11^th,August 2020

CORRECTION  TO LESSON 12

1 [a]Zinc  blend[ZnS]

 [ii]Gypsum [CaSO₄.2H₂O]

 [b][i]Monoclinic sulphur

     [ii]Rhombic  sulphur

[c]Allotropy is a phenomenon in which  an element  exist in two or more  forms in the  same physical 

State.

[d]Powdered  sulphur  is dissolved in carbon [iv] sulphide in a  beaker .The  solution is warmed

,and filterd   into another  beaker and allowed  to evaporate,when  yellow crystals  of  rhombic  sulphur

Are  deposited.

2[a][i]SO₂

      [ii]SO₃

[b]When SO₂ is passed  through water, trioxosulphate[iv] acid is  obtained.

SO₂  +H₂O —–>H₂SO₄.

[ii]H₂SO₄ acid  is  obtained  when  sulphur[vi] oxide is passed through water.

SO₃ +H₂O ——>H₂SO₄

[c]Sulphur [iv] oxide.

3[a][i]S  +O₂——>SO₂

   [ii]2SO₂  +O₂ —–>2SO₃

    [iii]SO₃  +H₂SO₄ ——>H₂S₂O₇

[iv] H₂S₂O₇  +H₂O——->2H₂SO₄

[b]Concentrated H₂SO₄ is  a strong dehydrating agent. It dehydrates ethanol and sugar as follows:

 [i]CH ₃CH₂OH –>C₂H₄

  [ii] C₁₂H₂₂O₁₁——->12C

LESSON 12

4^TH,AUG.2020

TOPIC;Questions based on Sulphur

Goodmorning  students,hope your weekend was good.Please do not relent,continue to work hard and success will surely be yours in Jesus name.Today,just want to remind us about SULPHUR.Remenber the  occurrence and nature of sulphur,i.e, it occurs free in nature as large yellow deposits, and in combination with  other elements viz:Galena[PbS],Zinc blend[ZnS],Iron pyrites[FeS₂] and so on.Allotropes,extraction,properties,uses and compounds of  sulphur.

Examination  questions

1[a]Name two natural ores of sulphur.

[b]Name two allotrotropes of sulohur.

[c]Define allotropy.

[d]How can you prepare a sample of rhombic  sulphur.

2[a]Name two oxides of sulphur.

[b]What is obtained when each of them is passed through water?

[c]Name one  bleaching agent.

3[a]With equations only describe  the preparation of tetraoxosulphate[vi] acid  by  the contact process.

[b]With examples describe the dehydrating  properties of concentrated tetraoxosulphate[vi] acid.

4[a]Describe  the  behavior of sulphur  as it is heated to  boiling point.

[b]With equations  only  show the reactions  of sulphur with the following;[i]O₂ [ii]H₂  [iii]Zn [iv]C [v]H₂SO₄

5[a][i]State and explain what happens  if hydrogen  Sulphide  gas is bubbled into  acidified  K₂Cr₂O₇.

[ii]State  the equation of the reaction.

[b]How  can you obtain a sample of  dry  hydrogen sulphide in the  laboratory?

    CORRECTION  TO LESSON  11

1.[i]Finely divided iron.

    [ii][a]Heat change

         [b]Pressure

    [iii]Zero

    [iv][a]It is a colourless gas.

          [b]It is very soluble in water.

     [v]3CuO  +2NH₃ —–à3Cu +H₂O  +N₂

2.[a][i]3H₂  +N₂  —–à2NH₃ Requires high temperature  and pressure in  the  presence of a catalyst of  iron impregnated with aluminium.

      [ii]N₂  +O₂  ——-à2NO

      [iii]3Mg  +N₂ —–àMg₃N₂

   [b]Haber  process

             This  is  the industrial  manufacture of ammonia.Hydrogen and  nitrogen in the ratio 3:1 by volume are purified, dried and  compressed at  a temperature of 600^oC  and a pressure  of 200 atmosphere.The  compressed mixture  is passed over  a catalyst of divided iron mixed with alumina.Ammonia  produced  is separated by washing  with  water.

3[a]The manufacture of trioxonitrate[v] acid  from ammonia takes place in three stages.They are

  [i]The catalytic oxidation of ammonia to nitrogen[ii]oxide[NO]

4NH₃  +5O₂ —-à4NO  +6H₂O.It is a reversible reaction and it  takes place at about 700^oC using a platinium-rhodium catalyst.

  [ii]Oxidation  of nitrogen[ii]oxide  to nitrogen[iv].

     2NO  +O₂ ——à2NO₂

  [iii]Reaction of nitrogen [iv]oxide with hot water to form trioxonitrate[v] acid.

3NO₂  +H₂O —–à2HNO₃      +NO.The nitrogen[ii] oxide obtained in the third stage reacts with more oxygen to form NO₂,which reacts with  more  oxygen to form NO₂,which reacts further with water to form trioxonitrate[v]acid.

[b][i]NaOH   +HNO₃  —–àNaNO₃ +H₂O

     [ii]CaCO₃  +2HNO₃  —–àCa[NO₃]₂   +H₂O +CO₂

   [iii]P +5HNO₃ –àH₃PO₄  +H₂O +5NO₂

   [iv]H₂S    +2HNO₃ —–àS +2H₂O +2NO₂

   [v]4Zn  +10HNO₃ —–à4Zn[NO₃]₂  +3H₂O  +NH₄NO₃

LESSON 11

28/07/2020

Topic;Questions based on Nitrogen and its compounds.

Good morning students,hope your weekend was fine.Ensure that all necessary corrections are checked.Today we will look at questions that cuts across Nitrogen and its compounds

Past questions based on  Nitrogen and its compounds

i.Consider the reaction represented by the following equation;

3H2  +N2 —->2NH3

[1]Name the catalyst  used nin the reaction.

[ii]State two measurable quantities which can be used respectively to derive  the value of G^o for the forward  reaction.

[iii]What will be the change in the free energy of the  system at equilibrium?

[iv]Give two physical properties of ammonia.

[v]Write an equation to show the reducing property of ammonia.

2.[a]With the aid of balanced chemical equations describe the reaction of Nitrogen with

     [i]Hydrogen.

     [ii]Oxygen; and

     [iii]Magnesium

    [b]Describe  the Haber process for the production of ammonia.

3.[a] Outline the manufacture of trioxonitrate[v] acid from ammonia.

    [b]With equations only,show the reactions of trioxonitrate[v]acid  with the following:

         [i]NaOH      [ii]H2S     [iii]CaCO3    [iv]Zn    [v]P

4.Describe  the laboratory preparation and properties of  Nitrogen[iv]oxide.Show  the chemical equation   of  the reaction with all the  necessary conditions.

5.[a]How can you obtain a sample of  lead from lead[ii]oxide?

    [b]Name  the gases given  out when silver trioxonitrate[v] is heated.

LESSON 10

21/07/2020

Good morning students,hope you are good. I observe that only few of you attempted lesson 9,so lesson 9 is repeated ,meaning attempt it as lesson 10.

LESSON 9

14/07/2020

Hello students,greetings to you all .Pls make sure all corrections are noted before attempting next lesson.

Finailly,we will take the last questions that cuts across question number 3 of WAEC chemistry practical

1[a]Explain briefly the observation in each of the following processes:

[i]When Carbon[iv]oxide is bubbled  through lime water,it turns milky  but the milkiness  disappears when the  gas is  bubbled for a long time;

[ii]A precipitate of calcium hydroxide is insoluble in excess  sodium hydroxide solution whereas that of Lead[ii] hydroxide is soluble.

[b][i]What is primary standard solution ?

[ii]Calculate the mass of  sodium trioxocarbonate [iv]  required to prepare 250cm³ of  0.15moldm^-3solution.[Na=23.0;O=16.0;C=12.0]

[c]Name one gas that can be  collected by:

[i]Upward displacdment of air;

[ii]Downward displacement of air.

 2[a]Write the electronic configuration of an element with atomic number 15, indicating the distribution of electrons in the energy sub-levels.

CORRECTION TO LESSON 8

1[a][i]Q is copper[ii] trioxocarbonate[iv]/CuCO3.

[ii]Carbon[iv]oxide.

[iii]Excess Q was used to ensure that all ther acid reacted.

[iv]When there is no effervescence.

[v]Filtration.

[vi]To form crystals/to concentrate the filtrate in order to form crystals on cooling or heating to dryness of CuSO4 would not be obtained/anhydrous CuSO4 will not be obtained.

[b][i]White anhydrous copper[ii]tetraoxosulphate[vi]/blue cobalt[ii]chloride paper.

[ii]Alkalin iodine solution/acidified potassium tetraoxomanganese [vii]/acidified potassium heptaoxodichromate[vi].

2[a]-Evaporating dish

-Bunsen burner

-Tripod stand

-Wire gauze

[b][i]Sodium trioxocarbonate[iv],Na2CO3

Potassium trioxocarbonate[iv],K2CO3

Sodium ethanoate,CH3COONa

Potassium ethanoate,CH3COOK

Potassium cyanide,KCN

Sodium Sulphide,Na2S

[ii]The phenimenon is Hydrolysis

[c][i]White precipitate,followed by effervescence and the precipitate dissolves in excess dilute HCL.

[ii]Sulphur[iv]oxide,SO2

Hydrogen Sulphide,H2S

Unsaturated gaseous hydrocarbon[C2H2,C2H4,C3H6,C4H8,C3H4,C4H6etc.][any one]

LESSON 8

07/07/2020

TOPIC;Questions cut across number 3 of both WAEC and NECO practicals

Hello students,how are you today.Please make sure, you check the corrections to previous lessons before attempting lesson 8.

Questions

1[a]In the laboratory preparation of crystals of CuSO4, a green powder Q was added to dilute H2SO4 and stirred.Effervescence occurred and a gas R was given off which turned lime water milky .Excess Q was removed from the mixture. The solution of CuSO4 was concentrated to half its original volume and allowed to stand.[i] What is substance Q?[ii]Name gas R[iii]Why was excess Q used?[iv]How would you know that the reaction is complete[v]What method was used to remove excess Q?[vi]Why was the solution of CuSO4 not heated to dryness?

[b]Name the reagents used for testing each of the following substances in the laboratory:[i] Water [ii]Primary aikanol.

2[a]List tree pieces of apparatus required for the evaporation of sodium chloride solution to dryness.

[b][i] List two normal salts which when dissolved in water turn red litmus blue.

[ii]State the phenomenon that is responsible for the action on the litmus in 2[b][i].

[c][i]State what would be observed on adding BaCl2 solution to a portion of a saturated Na2CO3,followed by dilute HCl in excess.

[ii]A gas Q decolourrized acidified KMnO4 solution.Suggest what Q could be.

CORRECTION TO LESSON 6

1[a]Colourless

[b]Blue

[c]Pink

2.To each of the solution add sodium hydroxide solution in drops then in excess[i]CuSO4 will give a blue precipitate insoluble in excess.[ii]FeSO4 will give a green precipitate insoluble in excess.

3[i]Y

[ii]X

[iii]Z

4 [i][a]Hydrogen sulphide

[b]Sulphur[iv]Oxide

[ii][a]Desicator

[b]Condenser

[c]Sublimation

2[a]Compound[s] which:

[i]has a black colour =MnO2

[ii]Is a basic Oxide=MnO2

[iii]Sublime on heating=NH4Cl

[iv]Dissolves in water to give a solution of pH less than 7=NH4Cl or Pb[NO3]2

[b]The colour of each of the following aqueous solution are:

[i]Caicium hydroxide=Colourless

[ii]Iron[iii]trioxonitrate[v]=Yellow or brownish yellow

[iii]Coppere[ii]tetraoxosulphate[vi]=Blue

[iv]Potassium hepataoxodichromate[vi]=Orange

[c]Neutral oxide which is colourless at room temperature=water

[d]

DATE;30/6/2020 lesson 7

Hello students,warm greetings to you and hope you are getting ready for resumption.All the best.pls ensure that all lessons are taken and assignments done ,it will do you good.

lesson 6 has not been done,so do that for 30/6/20,tuesday.

CORRECTION TO LESSON 4

[1]a[i]Calorimeter.

[ii]Hoffman voltameter.

b[i]Glucose is soluble in water while Cellulose is not soluble in water.

[ii] Glucose is a strong reducing agent;it reduces Fehlings solution to a red precipitate of copper [i] oxide on boiling.Cellulose does not reduce Fehlings solution.

2[a]i Y is a concentrated teraoxosulphate [iv] acid,while Z is hydrogen chloride gas.

[ii]Acidify a solution of X with dilute HNO3 and silver trioxonitrate [v] solution.White precipitate is formed which is soluble in aqueous ammonia.This confirms the presence of chloride.Alternatively,to the solution of X , add lead two ion solution to get a white precipitate which is soluble when hot and reappears on cooling.This confirms the presence of chloride.

b[1] Calcium chloride is used in the laboratory as drying agent.

[ii]The laboratory technique used is magnetization or dissolution in water and filtration.

3[a]i On bubbling SO3 into acidified KMnO4 solution , becomes decolourised; the purple colour of the solution disappears and it is discharged.

[ii] On mixing zinc dust with CuSO4 solution,the blue colour of the CuSO4 gradually disappears; the solution becomes colourless.A reddish-brown or pink deposit is obtained.

[iii] On adding concentrated HNO3 to freshly prepared FeSO4 solution, the solution changes colour from green to brown.

[b]Substances which ,if added to dilute H2SO4 would give:[i]Hydrogen-Magnesium/Iron/Zinc[ii]ZnSO4-ZnO/ZnCO3/Zn.

Chemistry  ss3      23/06/2020    lesson 6

Hello   students, how was your weekend? I  hope  to see you in school very soon as you remain safe .

Please attempt the following questions using the box provided:

1.State the colour observed when distilled water is added to each of the following: : 

       (a). Silver trioxonitrate( V) solution.

        (b). anhydrous copper(I I) tetraoxosulphate(V I)

         (c). anhydrous  cobalt (I I) chloride

2. Describe   one  wet  chemical test  that  could be used to distinguish between  CuSO4 and FeSO4

3. Use the table below to answer questions (a) to (c)

Indicator	PH range
X	3.2  – 4.4
Y	6.0  -7.6
Z	8.2  -10.0

Select from the list the indicators that would be suitable for titrating : ( i ) NaOH solution against HCL.

( i i ) NaOH Solution against CH3COOH (aq) .  ( iii ) HCL(aq) against NH3 (aq)

4.  ( I ) State one gas that can be tested for using each of the following  reagents :  (a) Lead (I I ) ethanoate  solution . (b)  acidified  potassium  tetraoxomanganate (I v ) solution

     (I I ). Name  one laboratory apparatus used for : (a) Keeping  solids dry  (b)  Changing  vapour  to  liquid  (c) . Name a suitable method  for obtaining  iodine  from a mixture of iodine and  sand.

2. (a) C onsider the following  compounds  MnO2 , NaHCO2 ,  NH2CL  and  Pb(NO3)2. Select the compound(s)  which  (  I )  has  black  colour  (i  i ) is a  basic  oxide ( ii i ) sublime on  heating ( i v ) on heating  (I v ) dissolves in water to water to  give  a solution  of  PH less  than  7 . 

    (b) State  the colour of  each  of   the   following aqueous  solutions  ; (i) Calcium hydroxixe ( i i ) iron  ( i i i ) trioxosulphate ( v )  ;( i i i ) Copper (I I ) tetraoxosulphate  (i v) . ( I v ) Potassium  heptaoxodiochromate ( v i )

      (c ) Give  one  example of a neutral oxidewhich  is a colouless  liquid  at room  temperature.

         (d ) Draw  and  label a diagram  for a set-up that can  be used  for  the  separation of  two  immiscible  liquids.

3. (a) State  an  indicator suitable  for the   titration  of  (i) dilute HCL  and  NaOH(aq) ; ( i i )  dilute  CH3COOH  and  KOH(aq)  ;  ( I I I ) dilute HCL  and  NH3(aq). Give  a reason  for your answer  in each case.

     (b) Calculate  the  volume  of  water  that would be added  to  50cm3  of  0.10mol dm3  of  HCL  to  dilute  it  to  0.010mol dm3.

     (c ) Name  one gas  that  could  be  used  to  demonstrate  the  fountain  experiment.

LESSON  5

DATE;16/06/20

Hello  students,hope you are doing great .By Gods grace  keep preparing hard for your exams and success will be yours in JESUS name.AMEN.

Lesson  4 will be repeated this week because ,I did not see any submission.Ensure    that  the  corrections  for  lessons 1,2,&3 is  properly checked,  so that you  will   be able to note your mistakes.  Pls  participate in all the lessons,do not assume  anything.God  bless You all..

      CORRECTION TO LESSON   3  SS3

1.Chlorine

2.Irritating smell

3.Does not burn in air or support combustion

4.Colourless but misty in damp air .

5.Turns red from  blue

6Nitrogen [iv] oxide

7.Does not burn or support combustion

8.Irritating

9.Splint burns

10.White fumes

11.Turns red from blue

12.Burning sulphur or burning match

13.Does not burn or support combustion

14.Colourless

15.Burns with blue flame depositing yellow  sulphur on cold surface

16.Turns faint red.

17.Colourless

18.Does not burn or support combustion

19. Turns red.

20.Colourless

21.Burns with blue flame,explodes if mixed with air

22.Odourless.

23.Rekindles glowing splint

24.Colourless

25.Does not burn or support combustion

26.Turns faint red

27.Colourless

28.Odourless

29.Does not burn or suooprt combustion

30.Colourless.

LESSON 4

DATE:09-06-20

Hello my students, I hope you are doing great. I have checked your submissions, most of you are still on lesson 1. Please make sure you attempt lessons 2&3 and the corrections will be sent. Today,we will be looking at questions that cut across no.3 for chemistry practicals.

1(a). Name one laboratory apparatus/set-up for

i. Determine the heat of neutralization

ii. Decomposing water into hydrogen and oxygen.

b. Outline a suitable procedure for distinguishing between glucose and cellulose using

i. One physical test a part from tasting

ii. One chemical test.

ci. Mention one salt which produces brown fumes on being heated strongly.

ii. What is the action of the brown fumes mentioned in ci above on litmus above?

iii. Give one reasons why it is not advisable to collect nitrogen by displacement of air.

2. A soluble chloride X reacted with a liquid Y on heating, to give gas Z which turned moist blue litmus paper red and fumed in moist air

i. Identify Y&Z

ii. Give one chemical test to confirm that X is a chloride

bi. State one laboratory use of calcium chloride

ii. Name one laboratory technique suitably for separating a mixture of iron filings and ammonium chloride without applying heat.

3a. State what you would see on

i. bubbling SO2 into acidified KMnO4 solution

ii. Mixing zinc dust with CuSO4 solution

iii. Adding concentrated HNO3 to freshly prepared FeSO4 solution

b. List two substances in which, if added to dilute H2SO4, would give you

i. H2(g)

ii. ZnSO4(AQ).

CORRECTION TO LESSON ONE

1 (a) (I) Blue- black

(11) Black

(111) Pink or Purple

(1v) Yellow

(b) Pass each gas separately through ammoniacal copper (1) chloride. Reddish-brown precipitate indicates ethyne. No precipitate indicate ethene.

2 (a) 1 Ammonia gives dense white fumes with concentrated HCL.

11 Test for the-COOH functional group add saturated NaHCO3 / Na2CO3 solution, effervescent or gas is evolved, or add alcohol and warm with a few drops of concentrated H2SO4. Sweet smell of ester occurs.

                                                                  SS3 REVISION LESSON  3

02/06/2020

Hello students, warm greetings to you and hope you are doing great.

TOPIC: QUALITATIVE ANALYSIS CONTINUES

When little of a given substances is  heated in an ignition tube or in a small hard test-tube until no further change  is observed ,gases usually  evolved from such substances .These gases are being  identified by:

[1]Noting  their  colours .

[11]Noting their odours

[111]Inserting in the gas ,a burning  splint.

[iv]Testing the gas with a moist red and moist blue  litmus paper to know if  the gas  is acidic or basic.

With the knowledge of identification of gasnues,fill in the spaces[1-30] in the table below as an assignment using the form  provided under the table,after suppling your name,class and Email.

GAS	COLOUR	ODOUR	ACTION WITH SPLINT	ACTION WITH LITMUS PAPER
1	Greenish yellow	2	3	Turns red then bleashes
Hydrogen Chloride[HCL]	4	Irritating  smell	Does not burn or support combustion	5
6	Reddish brown	Iritating ssmell	7	Turns red litmus  blue
Trioxonitrate iv]  acid vapour	Pale yellow Fumes	8	9	Turns red from blue
Tetraoxosulphate [vi] acid	10	Irritating	Does not burn or support combustion	11
Sulpuhur [vi] oxide	Colourless	12	13	Turns red
Hydrogen Sulphide	14	Rotten egg	15	16
Ammonia	17	Chocking	18	19
Hydrogen	20	Odourless	21	Not applicable
oxygen	Colourless	22	23	Not applicable
Carbon [iv] oxide	24	Faint and not easily detected	25	26
Water vapour	27	28	29	Not applicable
Nitrogen	30	Odourless	Does not support combustion	Not applicable

CORRECTION TO LESSON TWO

1 (a) (1) Only two of the metals, Zn and Fe will liberate a gas, H2 from one of the aqueous solutions, dilute hydrochloric acid. Of these metals , only Fe will form a green solution. Therefore, R is Fe .

Zinc will form a colourless solution because zinc Ione is colourless. Therefore, S is Zn . A!long the metals, only Cu will have no reaction with three of the aqueous solutions, FeSO4, CuSO4 and HCl, since copper is less active than Fe and H and will not displace its own ion. But Cooper will displace silver ion from AgNO3 forming a greyish- white deposit of silver. The light blue solution is CuSO4. Therefore, Q is Cu.The only other metal T is Pb.

(11) Only dilute HCl will give off a gas,hydrogen ,by reacting with the active metals Zn (S) and iron (R).That is B is dilute HCl.Of the four aqueous solutions only AgNO3 will form a greyish deposit of solid silver with Cu, Fe,Zn and Pb because all four metals displace silver ion in AgNO3 ,since all are more active than silver.Therefore D is AgNO3.

The brownish deposit of R,S,And(I.e.Fe,Zn,andPb)in C is due to Cu deposited from CuSO4 because both Fe,Zn and Pb are more active than Cu.Therefore C is CuSO4.The remaining aqueous solution A must be. FeSO4.

(111)The gas evolved is Hydrogen. It can be tested by bringing a lighted splint near the mouth of the test-tube.A pop sound due to explosive burning of hydrogen in the air, indicates hydrogen.

(b)Other anions such as trioxosulphate(iv) and triocarbonate(iv) also form white precipitates with bariumchloride solution. But these white precipitates are dissolved by dilute HCl acid.Therefore,acidifying the unknown solution with dilute HCl acid eliminates trioxosulphate(iv)ion and triocarbonate(iv) ion when a white precipitate is formed on addition of bariumchloride solution, leaving tetraoxosulphate (vi) ion.

(2) Note that since both are trioxonitrate(v) salts the selected should be to distinguish between ammonium ion sodium ions.

Put about 2g of each in a separate test-tube. Add NaOH(AQ) to each and warm. Where a gas is given off with irritating smell and turns wet red litmus paper blue. The gas is NH₃ and salt is NH₄NO₃ . where no gas is given off the salt is NaNO₃.

(b) Note that the basic difference between the is that why cyclohexene is an unsaturated cyclic hydrocarbon, ethanoic acid is a saturated alchanoic acid. They are both liquids hence,the test chosen is either

(I) test for unsaturation or

(I) test for acidity.

To 2cm³ of each liquid in a test-tube add bromine water. The one that decolourises is cyclohexene while the one that does not dicolourise bromine water is ethanoic acid OR to 2cm³ of each liquid in a test-tube add saturated NaHCO₃ solution. Where effervescence occurs and gas evolved turn Lime water milky, the liquid is ethanoic acid, where no gas evolved the liquid is cyclohexene.

(C) Note that since both are salts of calcium, the test chosen will be to distinguish between Cl^– and CO₃^2-. Put about 2g of each I’m separate dry test-tubes. Add dilute HCL to each. Where there is effervescence with evolution of a colourless gas that turns lime water milky, the reagent is CaCO₃. Where there is no visible reaction, the reagent is CaCl₂.

(d) Note that both are salts of sodium. Test should distinguish SO₃^2- from SO₄^2-. Make a solution of each. To 2cm³ of each in a test tube add dilute HCL. Then add BaCl₂ solution to each. The one that forms a white precipitate insoluble in excess dilute HLC is Na₂SO₄.while the one whose precipitate dissolves in excess dilute HCL is Na₂SO₃.

(3) To the unknown solutions add few drops of NH₃ solution dropwise and later in excess. White gelatinous precipitate soluble in excess confirms Zn²⁺ while white gelatinous precipitate insoluble in excess confirms Al³⁺.

(bi) dilute H₂SO4

(bii) ammonia solution

(biii) concentrated tetraoxosulphate (vi) acid or concentrated tetraoxophosphate(v)acid.

(c) effervescence occurs with the evolution of a colourless gas.

LESSON TWO DATE;20/05/20

Hello students,how are you doing and your studies?do stay safe.

Topic;QUALITATIVE ANALYSIS [continuation]

No Fields Found.

LESSON ONE

Hello students,hope your day is fine and you are coping with the present situation in the world ,ensure you stay safe.

We shall have more of revision and past questions from different topics on this platform.

Topic Date delivered:14/05/20

QUALITATIVE ANALYSIS

This process is used to identify the type of particles(not the amount of substances) present in a chemical sample. It can be used to identify the type of cations ,anions, gases or functional group (s) present in a given sample.

The method involves physical appearance (colour), observation (flame test), heating (identification of gases) and the use of some chemical reagents.

For identification of cations,(basic radicals), NaOH and ammonium hydroxide are the most common reagents used, the solubility or insolubility of the cations in these reagents during the analysis, deep on the particular cations present, which eventually will be confirmed., other reagents are sometimes added.

For anions (acidic radicals), the most common reagents are dilute trioxonitrate ( iv) acid,silvertrioxonitrate (iv)and ammonium hydroxide (for chloride test),Iron(11) tetraoxosulphate(vi), conc.tetraoxosulphate (vi) acid(for trioxonitrate(v)( ion test), dilute trioxonitrate(v) acid, or dilute HCl,lime water(for triocarbonate (v) iron and carbon (iv) oxide)bariumchloride, bariumtrioxonitrate(v), dilute HCl and potassiumtetroxomanganate (vii) or potassiumheptaoxodichromate(vi) (for tetraoxosulphate (vi) ion, trioxosulphate(v) ion and sulphor (iv)oxide gas test). The different anions give different observations, leading to the confirmation of the actual one (s) present.

For organic compounds, the following reagents are used for testing, water, saturated, sodiumhydrogentrioxocarbonate(iv) ,NaOH, HCl(dilute), brome water, alkaline potassium tetraoxomanganate (vii), ethanoic acid, conc.tetraoxosulphate (vi) acid ,ethanol, Fehling’s reagents, iodine solution.

Revision Questions

1 (a) State the colour of

(I) starch on reacting with iodine;

(ii) manganese (IV) oxide powder;

(iii) phenolphthalein indicator in a solution of pH 10; and

(iv) the colloidal suspension formed when dilute hydrochloric acid is added to sodiumtrioxothiosulphate(vi)solution.

(b) Give one chemical test to distinguish between ethene and ethyne.

2. (a) I. State what is observed when ammonium is tested with conc.HCl.

ii Give one chemical test for – COOH functional group.

Fill the following below; Your name in the appropriate box,Email address,subject and answers[both in the message box].

No Fields Found. No Fields Found.