ةلديص ناسرف ةرسا……………..pharmaza ... - Weeblyhishamezzat.weebly.com/uploads/9/0/6/0/9060375/final_anion22012.pdf · ةلديص ناسرف ةرسا……………..pharmaza…………..ةلديص

..…………pharmaza..…………… اسرة فرسان صيدلة اسرة فرسان صيدلة …..…..pharmaza

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1. How can you analysis mixture of :

Carbonate and Bicarbonate.

Chloride & Bromide & Iodide.

-


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-Sulphide & Sulphite & Thiosulphate & Sulphate.

2.WRITE SHORT NOTES ON :

Hepar's Test.


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-Cholrine water Test.

3.Discuss the following :

- Boron Fluoride Test

-BF3 gas turns the

flame Colour into

............... while CO

gas turns it into

............


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Chromyl Chloride Test-

4.How can you analysis

- Mixture of Nitrate and Nitrite .

1- Test for nitrite with any oxidizing agent

2- Removal of nitrite by converting to N2

3- Test for NO3-


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- Mixture of Nitrite and Bromide or Iodide.

5. - The main difference between ferro- and ferricyanide

concerning with their reactions with sulphoric acid is


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6- By equation Only Give the Action of Silver nitrate on cyanide

, Thiocyante

7. Write short notes on :

-Difficulties of oxidizing agents.

Sources of the difficulty:

1) On passing H2S gas to precipitate the cations of gp. II; the reagent

then decomposed into colloidal sulphur which retard filtration and

consequently the group is not completely precipitated.

H2S + (O) oxidizing agent H2O + Sa.

2) Non-volatile oxidising agents, e.g. arsenate, and antimonate would

precipitate Ca2+, Sr2+, Ba2+ (gp. V), (gp. IV) and Mg2+, together with

gp III when render the medium alkaline with NH4OH to precipitate

iron group.

Tests of oxidizing agents.

1- Mixture + HCl conc.: Cl2 gas is evolved (Tested by litmus paper).

2HCl + (O) = H2O + Cl2

2- Mixture + dil. HCl, pass H2S: Yellow colloidal sulphur

H2S + (O) = H2O + So

3- Manganous chloride test: solution + conc. HCl acidic + MnCl2

solution in conc. HCl boil

brown or black colour (MnCl4 or

(MnCl6)2). Arsenate and nitrite give negative test.


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4- Kl-test: solution + H2SO4 acidic + CHCl3 + Kl then shake

violet

colour in the organic layer.

2KI + 2H+ + (O) = H2O + I2 + 2K+

Note: (NO-2, Fe3+ Cu2+ and other oxidizing cation may give +ve test).

5- Special tests for each radical: e.g. arsenate.

Removal of the oxidizing agents-Difficulties:

These are several methods for removing the difficulties, all those

used methods apply a suitable reducing agent.

1) H2S method: As usual to test group II pass H2S continuously to

precipitate group II as sulphides and reduce the oxidizing agent into

another non-oxidising form e.g.

2F3+ + H2S = 2H+ + 2Fe2+ + So

Disadvantages:

a) Colloidal sulpur (So) is formed which could be cured by boiling with

filter paper bulb or drops of HNO3 is oxidize it into SO2.

So + (O) HNO3 SO2

b) Some H2SO4 may be formed leading to the precipitation of the insol.

Sulphate of Ba2+ & Sr2+ (gp. V) and Pb2+ in gp. 11.

2) SO2 method: Specially for MnO4 and Cr2O2-7

SO2 + H2O = H2SO3 )O(

H2SO4

Disadvantage: Some H2SO4 produced giving insol. Sulphates of Pb2+ and

Sr2+.

3) Conc. HCl method: Used either with the solid mixture of with the

filterate from gp I by boiling with HCl till no more Cl2 evolves as tested by

KI/starch paper. It is generally used for MnO4 and Cr2O2-7.

2KMnO4 + 16 HCl = 8 H2O + 2KCl + 2 MnCl2 + 5 Cl2

4) Ethyl alcohol method: Used for MnO-4 and Cr2O2-

7, the alcohol is

oxidized partially into acetaldehyde in the presence of HCl.

CH3 . CH2 . OH )O(

CH3 . CHO + H2O

5) Hl or ammonium iodide method: Specially for AsO43-:

Procedure: Filterate from gp 1 + 1 ml 10% NH4l. + 4 ml conc. HCl justheat

and pass H2S till complete precipitation and filter:

NH4I + HCl = NH4Cl + HI


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=> Write short notes on : - Source of Difficulty& The removal of phosphate.

1. Source of Difficulty: On a king the solution alkaline for precipitation,

the sparingly soluble phosphates of this group, group IV, and group V

together with Mg2+ will precipitate.

2. The removal of phosphate Difficulty:

1) Basic acetate method: This method depends on the facts:

i) Phosphates group III-V and Mg2+ insoluble in water and in

NH4OH.

ii) All phosphates are soluble in

iii) All phosphates are soluble in acetic acid except group III-

phosphates (i.e. selective solvent).

iv) The addition of amm. acetate solution to a solution containing

Fe3+, Al3+ and Cr3+ yields the acetates of these metals.

v) FePO4 is cream yellow in colour and insoluble in water while ferric

acetate is red and soluble in H2O giving red solution.

vi) FePO4 is soluble in excess ferric solutions.

vii) If a solution of Fe (CH3COO)3 is diluted and boiled, the iron is

quantitatively precipitated as the brown basic acetate

viii) Ammonium acetate acts as buffer and neutralizes the free acids

and also acts as an indicator.

Procedure:

a) Boil the filtrate from the group II to drive off H2S.

b) Test for the presence of iron and phosphates, if iron presentm

oxidize the whole solution by boiling with nitric acid.

c) Add 1-2 gm NH4Cl, then add NH4OH solution slowly till just alkaline,

a faint permanent turbidity is formed.

d) Add dil. HCl drop by drop, string after each addition till the ppt.

formed just redissolves.

e) Add 1-2 ml of dilute acetic acid (1:1) and (3-4) ml of saturated

ammonium acetate solution.

f) The solution is now either:

i) Red: This means that iron is more than PO3-4 if so, add 10%

PO4 solution drop by drop till the precipitate formed is just

yellow to a red thinge (buff coloured ppt.)


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ii) Not red: This means that PO3-4 is more than iron, add neutral

5% FeCl3 drop by drop till a red ting is just produced on the

precipitate.

g) Test the equilibrium by dilution and boiling a portion of the solution

and filter, render alkaline with NH4OH, if a white ppt. obtained, this

indicates the presence of excess phosphate, while the formation of

red ppt. indicates excess iron, in either cases, repeat the

adjustment process till equilibrium state i.e. neither red nor white

ppt. must be formed.

h) After equilibrium, dilute to about 50 ml with water and boil the

solution for one minute and filter white hot.

3) Ferric chloride method.

4) Metallic tin method.

5) Stannic chloride.

6) Na2CO3 method.

7) Ziroconium phosphate method.

=> Write short notes on : Sulphur fusion test:

One part of the insoluble, is mixed with one part of sulphur and 4

parts of fusion mixture (equal parts of K2CO3 and Na2CO3) is placed in an

ignition tube or crucible, fuse the mixture, cool, and extract with boiling

water and filter.

Acidify the filtrate with dil. HCl if a yellow ppt. is formed which is

soluble in oxalic acid SnS2 (from SnO2)

2SnO2 + 9So + 2 Na2CO3 2NA2SnS3 + 2CO2 + 2 SO2

Na2SnS3 + 2HCl = SnS2 + 2NACl + H2S

If orange ppt insoluble in oxalic acid and sol. In tartaric acid, i.e. Sb2O5

=>Write short notes on : - Fusion mixture test:

Equal parts of Na2CO3 and K2CO3. (It fuses at a lower temperature

than each single salt). It is similar to the prepared solution in the acid

redical analysis (double decomposition). The main idea of this test is to

form the sodium or potassium slats of the acid radicals and to form the

carbonate of the basic radicals, with the exception of the amphoteric

metals as aluminium, which on fusion with the alkaline mixture it gives the

soluble NaAlO2.

BaSO4 + Na2CO3 BaCO3 + Na2SO4

SrSO4 + Na2CO3 SrCO3 + Na2SO4

4Al2O3 + 3 Na2CO3 6NaAlO2 + Al2 (CO3)3


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=> Write short notes on : Acid fusion: If the insoluble was dark red in colour it may be Fe2O3. Melt NaHSO4

or KHSO4 with a speck of the insoluble for few minutes, cool and extract

with water and filter.

2KHSO4 K2SO4 + H2SO4

3H2SO4 Fe2O3 Fe2(SO4)3 + 3H2O

The freshly eliminated H2SO4 dissolves Fe2O3.

Test for Fe+++ by NH4CNS.

- Write short notes on: Oxidising fusion:

If the insoluble is green it may be Cr2O3. One part of the insoluble

+ 1 part NKO3 + 4 parts fusion mixture are melted for 5 minutes in an

ignition tube, cool, extract with boiling water, filter and test for chromate

in the yellow filtrate.

Cr2O3 + 2 Na2CO3 [O]

KNO3 2Na2CrO4 + 2CO2

Acidify the filtrate with acetic acid boil off CO2 add AgNO3 brick

red ppt. (Ag2CrO4) or Pb acetate yellow ppt. (PbCrO4). Confirm the

presence of chromate by perchromic acid test.

=> Write short notes on : - Elimination of the difficulty of organic

matter.

1. Compete ignition: till it completely decomposes, but, certain metals are

converted into their insoluble oxides which is a new difficulty.

2. Incomplete ignation: till starting to decompose, then 1 to 2 HCl conc. Are

added and repeat the process, but silicates and Al2O3 may be formed.

3. Heating with HNO3 + H2SO4 (but BaSO4 and SrSO4 are formed) this

method can be used if the insoluble are taken separately and treated.

4. Heating with KCIO3 + HNO3 or KNO3: but explosion may occure and a

potassium radical is introduced.

5. Evaporation with HNO3: repeatedly till the black residue is completely

oxidized. Strong heat is not advisable as Fe2O3, and Al2O3 are formed

which are insol. In HCl.

6. NH4NO3 method: In an evaporating dish, take 0.2 gm of the mixture,

heat gently on a very small flame till carbon separates, cool, mix with 0.5

gm. NH4NO3, heat gradually till white fumes evolve and the mass got dry.

This procedure is repeated till no more organic matter is present.


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- Choose the right answer :

1. Ammonium molybdate test fails to give with :

a) AsO4-3 b) PO4

-3 c) AsO3-3

2.Upon heating with conc H2SO4 , agas evolves which burns with blue flame.

a) [Fe(CN)6]-3 b) CNS- c) CN- d) both a & c

3. Phosphine gas is :

a) PH3 b)PH4 c)PH5

4.Oxidizes S2O3-2 to S4O6

-2 :

a) Fe+3 b)I2 c)H2o2 d) both a & b e) All of the above

5. A coloures product easily decomposed by heat :

a) [Fe(SCN)6]-3 b) [Fe(NO)]+2 c) All of those

6.Wheen heated with persulphate gives aprecipitate of its peroxide:

a) Pb+2 b)Ag+ c) Fe+3 d) both a & b

7. Dimethylglyoxime is used to test for :

a) S++ b) Fe+3 c) None of these

8.SO2 gas has :

a)reducing action b)oxidizing action c)complexing action d)none of these

9.Chromyl Chloride gas is

a)CrOCl2 b)Cr2O2Cl c)CrO2Cl2

10.Oxidizing fusion mixture is used to test for :

a)Fe2O3 b)Al2O3 c)Cr2O3 d) None of these

11.Red lead (Pb3O4) is used to test for :

a)PO4+3 b)Cl c) None of these

12.After boiling it gives white precipitate with BaCl2 insoluble in dilute Hcl

a)S2O3-2 b)HCO3

- c)Both a & b d) None of these

13.The reagent that will differentiate between S-- and SO4-2 is :

a)HNO3 b) NH4OH c)Boiling water d)None of these


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14.Potassium chromate reacts in acetic acid medium with

a)Cl b)Br c)None of these

15.Brown ring test fails to give with:

a)NO2- b)ASO4

-3 c)NO3-

16.Acid fusion mixtureis used to test for :

a)Fe2O3 b)Al2O3 c)Cr2O3 d)None of these

17.Thiocynate ion forms coloured stable complexes soluble in either with :

a)Co+2 b)Cu+2 c)Fe+3 d)Both a and c

18.Silicic acid is :

a)H2SiO6 b)H2SiO3 c)H2SiO4

19.Decomposes nitrite with evolution CO2 :

a)Urea b)CO3-2 c)Sulphamic acid d)both a & b

20.Agcl dissolves in NH3 forming :

a)Ag(CN)2- Complex b)AgOH c)Ag2O d)None of These

21.Sulfuric acid has :

a)Reducing action b) oxidizing action c)dehydrating action d) a &b

e) b &c i)None of these

22.Magnesia mixture consists of :

a)MnCl2 + NH4Cl + NH4OH

b)MgCl2 + NH4Cl + NH4OH

c)MgCl2 + NH4HCO3 + NH4OH

d)None of these

23.Fe+3 Forms red colour complex with :

a)CN- b)SCN- c) S2O3-2 d)None of these

24.Conc. sulfuric acid reacts with Cl- producing :

a)HCl b) HCl + Cl2 c)Cl2 d)None of these

25. NO2- can be removed by treatment with:

a)Urea b) SO2 c)HNO3 d)None of these


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Complete the following:

1. The presence of Arsenate will Cause the difficulty -----------------------

--------------------------------------------------------------------------------.

2. The difficulty is removed by -----------------------------------------------

-------------------------------------.

3. Thiocynate ion is used to detect Fe+3 , Cu +2 & Co+2 ( Give the equation ,

colour of the product )

-----------------------------------------------------------------------------------

--------------------------------------------------------------------

4. The Addition of Ag+ ion to amixture of Cl- , Br- & I-

-----------------------------------------------------------------------------------

------------------------------------------------.

5. The sulfur fusion test (Insoluble) is carried out by

-------------------------------------------------------This can detect by ------

6. Iodide ions can be used to detect No2-- - Give equation

Zagazig University Faculty of Pharmacy

Anal. Chem. First year, 2nd term, Date: 02.06.2011

Time allowed : 1 hour Total marks: 30 marks

ملحوظة هامة : اإلمتحان على صفحتين

أجب عن جميع األسئلة

I- Write true (√ ) or false (X): 1- Dil. HCl can be used to differentiate between halides group and carbonate group ( ) 2- BaCO3 is water insoluble while BaSO3 is water soluble ( ) 3- BaCl2 can be used for separation of carbonate from bicarbonate ( ) 4- Sulphide can be reduced to sulphur or sulphate according to the used reducing agents ( ) 5- Dil.HCl can be used to differentiate between S2-, SO4

2-, S2O32- and SO3

2- 6- AsO4

3- acts only as oxidizing agent while AsO33- can act as reducing and

oxidizing agent ( ) 7- Nitrite ion can act as reducing and oxidizing agent while nitrate acts as reducing agent only ( ) 8- I- and Br- interfere with the brown ring test for arsenate ( ) 9- Acid fusion test can be used to detect Cr2O3 ( ) 10- Chlorate and bromate are oxidizing agents ( ) 11- Oxidizing agents can be tested by conc. HCl ( ) 12- All phosphates are soluble in mineral acids ( )

(0.5 x 12= 6 marks) II- A- Give reason for each of the followings:


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1- The reaction of ferric chloride with thiosulphate gives purple colour which disappears with boiling 2- According to the amount of HI the product of its reaction with Sulphuric acid will be different 3- A paper wetted with starch and I2 cannot be used for differentiation between SO2 and H2S gasses 4- Upon heating of silver Ferrocyanide ppt with conc. nitric acid, its white colour changes to orange red ppt 5- Before we make test of SCN- with iron, F- and Hg2+ should be absent 6- Reaction between Cu++ and I- gives white ppt in a brown solution B- Give one analytical use for each of the followings (for what and result only): 1- Magnesia mixture 2- FeSO4 (8 X 1 = 8 marks) __________________________________________________ III- Complete the followings: 1- The chemical structure of tetrathionate is ....................and of Hydrofluoro silicic acid is ................................ 2- CrO2Cl2 + OH- ====== ………….. + ………………. + ………….. 3- AsO3

3- + 2I- + 2H+ === ....... + ....... + ........ 4- NO3

- + 4 Zn° + 7 OH- === ....... + ...... + .......... 5- One difficulty caused by presence of arsenate is ……………………. and one method to remove the difficulty of arsenate presence is ………………….. 6- Sulfur fusion test is carried out to detect ………………(6 X 1 = 6 marks) __________________________________________________________ IV- Give short notes about the followings: 1- Differentiation between silver halides through their colours and their solubility in NH4OH (table form) (2 marks). 2- Analysis of a mixture containing NO2

- and NO3- (2 marks)

3- Removal of phosphate difficulty (3 marks) 4- Identification of Al2O3 insoluble (3 marks)


Anal. Chem. First year, 2nd term, Date: .06.2011

Time allowed : 1 hour Total marks: 30 marks

x 9 √ 5 √ 1

√ 10 √ 6 x 2

√ 11 x 7 √ 3

√ 12 x 8 x 4


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II- A- Give reason for each of the followings:

1- The reaction of ferric chloride with thiosulphate gives purple colour which

disappears with boiling: Due to formation of ferric thiosulphate complex

(purple colour) and upon boiling it converts to Fe2+ and tetrathionate (S4O6-

-) which are colourless.

2- According to the amount of HI the product of its reaction with Sulphuric acid

will be different : 2 HI + H2SO4 ===== I2 + SO2 + H2O

4HI + H2SO4 ======= I2 + S + H2O

6 HI + H2SO4 ======= I2 + H2S + H2O

3- A paper wetted with starch and I2 cannot be used for differentiation between

SO2 and H2S gasses: Because both of them has reducing characters leading

to disappearance of blue colour of the paper.

4- Upon heating of silver Ferrocyanide ppt with conc. nitric acid, its white

colour changes to orange red ppt: Because HNO3 acid acts as oxidizing

agent leading to oxidation of silver ferrocyanide (white) into silver

ferricyanide (orange red).

5- Before we make test of SCN- with iron, F- and Hg2+ should be absent: Because

F- reacts with Fe3+ and Hg2+ reacts with SCN- leading to decrease the

sensitivity of the reaction.

6- Reaction between Cu++ and I- gives white ppt in a brown solution:

due to formation of Cu2I2 (white ppt) and I2 (brown solution)

B- Give one analytical use for each of the followings (for what and result

only):

1- Magnesia mixture

Identification of phosphate and arsenate anions giving white ppt (give no

ppt with arsenite anion).


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s used for identification of nitrate or nitrite in brown ring test i: 4 FeSO -2

respectively giving brown ring. (Also it can be 4SO2using conc. or dil. H

). (Also it can be used for -3]6and [Fe(CN) -4]6, [Fe(CN)-used for test of SCN

in Fenton test for tartrate organic matter)

(8 X 1 = 8 marks)

__________________________________________________________

III- Complete the followings:

.and of Hydrofluoro silicic --6O4SThe chemical structure of tetrathionate is -1

6SiF2Hacid is

O2+ 2 H -2 Cl+ - -4CrO====== -+ OH 2Cl2CrO -2

No reaction=== ++ 2H -+ 2I -33AsO -3

O2+ H -2+ [ZnO2] 3NH=== -+ 4 Zn° + 7 OH -3NO -4

s the 2on passing H One difficulty caused by presence of arsenate is -5

reagent decompose into colloidal sulfur which retard filtration and no

++and Sr ++, Ba++cipitation (or it will cause precipitation of Cacomplete pre

of group V together with group III) and one method to remove the difficulty of

I or HI)4S (or NH2use of Harsenate presence is

)5O2(or Sb 2SnO Sulfur fusion test is carried out to detect -6

__________________________________________________________

IV- Give short notes about the followings:

Differentiation between silver halides through their colours and their solubility -1

.(2 marks) OH (table form) 4in NH

OH4AgCl white ppt soluble in dil. NH

OH4AgBr pale yellow ppt sparingly soluble in dil. NH

OH4and soluble in conc. NH

OH and 4AgI yellow ppt insoluble in dil. NH

OH 4sparingly soluble in conc. NH

(2 marks) -3and NO -2Analysis of a mixture containing NO -2

or Brown ring 4presence with KMnO -2At the beginning make test for NO -

test


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because it interferes with all reactions -2After that we must eliminate NO -

Cl 4his elimination can be done through boiling with urea or NH, t-3of NO

then heating) 4SO2(or make brown ring test using dil. H

as brown ring test in -3we can make test for NO -2After removal of NO -

nc in (or making Ammonia test using metallic zi 4SO2presence of conc. H

alkaline medium).

3. Removal of phosphate difficulty (3 marks) Answer pp 28 4- Identification of Al2O3 insoluble (3 marks)

First Question:

Mark (√) for the correct statement and (x) for the wrong one: (6 points)

1- Oxidation process is loss of electrons and Oxidizing agent losses electrons (X)

2- When KMnO4 reacts with thiosulphate, permanganate acts as reducing agent while

thiosulphate acts as oxidizing agent ( X)

3- Sulphite anion has reducing properties while persulfate anion has oxidizing

properties (√)

4- BaCl2 solution can be used for differentiation between S03--, CO3

-- and S04-- (X)

5- In mixture containing I-/Cl-, addition of Cl2 water drop wise in presence of CHCI3

will give violet, colourless, brown then colourless organic layer (X )

6- Oxalate and tartrate interfere with the reaction of CNS- with FeCl3 (√)

7- Boiling of thiosulfate anions with HCl leads to formation of yellow colloidal

precipitate of phosphorous (X)

8- AgI > AgBr > AgCl in solubility product (X)

9- For separation of mixture containing thiocyanate, ferrocyanide and ferricyanide

ions the first step includes addition of FeCl3 (√)

10- Hepar test is specific for S04-- and it depends on reduction of S04

-- to S° using

charcoal (X )

11- Addition of CdCO3 is the first step in separation of mixture containing S--, S03—

and SO4-- (√)

12- Formation of oily appearance during reaction between F and H2S04 in presence of

wetted glass rod is due to formation of silicic and hydrofluorosilic acids (√)

Second Question: Complete the following sentences (9 points)

1- Upon heating of silver ferrocyanide ppt with HNO3 its white colour converts into

orange red colour due to ferrocyanide is oxitlized with HNO3to ferricyanide which is

orang e in colour

2- Cr2O7-- + 3 SO3

-- + 8 H+ = Cr3+ + SO4-- + H2O

3- 2 [Fe(CN)6]3- + I- = [Fe(CN)6]

4- + I2

4- Chemical formula of cyanate is CNO- and of Prussian blue is Fe4[Fe(CN)6]3

5- BF3 gives the flame green colour while CO gives the flame blue colour

6- 2[Fe(CN)6]4- + Cl2 = 2[Fc(CN)6]

3- + 2 Cl-


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7. In presence and absence of sulphurous acid Cu++ reacts with SCN- giving different

results because (Write two equations)

in absence of sulfurous acid: Cu++ + SCN- = Cu2(SCN)2 White + H+ + SO4--

in presence of sulfurous acid (which is reducing agent prevent formation of (SCN)2

cu++ + H2SO3 + SCN- + H2O = Cu2(SCN)2 white + H+ + SO42-

8- Starch/I2 paper can not be used for differentiation between SO2 and H2S due to

both have reducing characters leading to disappearance of blue colour

9- A- To analyze mixture of Cl-/Cl2 metallic mercury should be used to remove the

interference of Cl2 with test of Cl- Cl2 + Hgo = Hg2Cl2 (ppt)

B- l- is the strongest reducing agent in halides because it is the lowest halide in

electronegativity

(l) Bromide and chloride mixture:

For Cl- carry out chromyl chloride test on a solid sample. Pp 24

For Br- chlorine water test pp 23

(2) Nitrate and nitrite mixture? Pp 24

(3) Arsenate and phosphate mixture pp 18

Give short notes on all the following

(1) Detection and removal of oxalic acid difficulty:

Detection

2 ml of solution + dil. HAc, warm to decompose any sulphites or thiosulphates ( filter

if necessary, to the filterate add l ml of calcium nitrate solution, the ppt. of calcium

oxalate is filtrated and washed and confirmed by KMnO4 decolourisation.

Removal

l- Complete ignition: till it completely decomposes.

2- Incomplete ignition till it starts to decompose then conc. HCl is added and repeat

the process1.

3- Heating with HNO3 + H2SO4.

4- Heating with KClO3 + HNO3 or KNO3 but explosion may be occure. Evaporation

with HNO3 till the black residue is completely oxidized.

5- NH4NO3 method: in an evaporating dish. take O2 gm of the mixture and heat on

very small flame till all carbon separates, cool, mix Will 0.5 gm NH4NO3, heat

gradually till white fumes evolved and the mass

(2) Detection and removal of potassium permanganate difficulty:

Detection

1. Mixture + HCl conc.: Cl2 gas is evolved (Tested by litmus paper).

2HCl + (O) = H2O + Cl2

2. Mixture + dil. HCl, pass H2S: Yellow colloidal sulphur

H2S + (O) = H2O + So

1- Kl-test: solution + H2SO4 acidic + CHCl3 + Kl then shake

violet colour

in the organic layer.


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2KI + 2H+ + (O) = H2O + I2 + 2K+

Removal

l- Cone HCl method: used either with the solid mixture or with the filterate from gp I

by boiling with HCI till no more Cl2 evolves as tested by KI/starch paper.

2 KMn04 + 16HCl = 8H20 + 2KCl + 2 MnCl2 + 5C12

2- Ethyl alcohol method: the alcohol is partially oxidized into acetaldehyde in the

presence of HCl-.

CH3.CH2.OH + (0) = CH3.CHO + H2O


Analytical chemistry-First year- second term exam 25May 2012

Time allowed 1 hour 30 points

Notes:

1. All questions must be attempted

2. Illustrate your answer with balanced equations whenever possible

First question: How can you proceed to analyse both the following mixtures:

1. Sulphate, sulphite and sulphide

2. Chloride, Bromide and iodide 10 points

Second question: Discuss both the following:

1. Test for oxidizing substances

2. Acid fusion test 10 points

Third question: Put false (x) or true (√) for the following sentences:

1. All carbonate and bicarbonate salts are soluble in water ( )

2. Fuming of sulphuric acid is a solution of S203 in H2SO4 ( )

3. HF is stronger acid than HI ( )

4. Stulfites and thiosulfates give white ppt. with BaC12 ( )

5. All Na, K, and NH4 salts of sulfides are insoluble in water ( )

6. Turnbulls blue ppt is produced from ferrocyanide and FeSO4 reaction ( )

7. Precipitate of pbx2 are formed on hot when halides are treated with lead acetate

( )

8. excess Iodides give yellow — scarlet red ppt with HgC12 ( )

9. Brown ring is formed when nitrate is reacted with FeSO4 solution ( )

10. Bettendorf’s test is special test for arsenates

11. yellow ppt is produced from phosphate reaction with H2S ( )

12. All Cyanides are water soluble except mercuric cyanide ( )


23

13. Fluorides and chlorides give white ppt with AgNO3 which is sol in KCN(

)

14. CO2and SO2 have reducing character

15. Diluted solutions of S208,can give white ppt with AgNO3 on cold ( )

16. Sulfides react with AgNO3 to give black ppt which is soluble in ammonia

and KCN ( )

17. Hydrogen. Carbonates react with BaCl2 on cold giving white ppt ( )

18. S2O3 react with pbAc to give white ppt which turns brown on boiling ( )

19. Chromyl chloride test is specific test for bromide( )

20. Prussian blue test is special test for HCl acid ( ) 10 points

Answer: Q1

1. Sulphate, sulphite and sulphide pp 22

2. Chloride, Bromide and iodide pp 21

Q2

1. Test for oxidizing substances pp 26

2. Acid fusion test pp 30

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