ss practical

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MALVIYA NATIONAL INSTITUTE OF TECHNOLOGY

DEPARTMENT OF CHEMISTRY

B.Tech. (1st Year) Practical Manual

2014-15

Jawaharlal Nehru Marg, Malviya Nagar, Jaipur, Rajasthan 302017

Phone: 0141 271 3301

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CHEMISTRY LABORATORY RULES AND SAFETY PRECAUTIONS

Never work alone in the laboratory. Keep your seat and surroundings clean. Do not throw pieces of paper and other dirty matter on the seat or on the floor. If

anything is spilled on the table, at once clean it with a duster. Never throw a burning match-stick or paper in the water box. Negligence may

cause fire. Handle all apparatus with care. In case of breakage, at once inform the teacher. Know the location and use of the fire extinguisher, safety showers and first aid kit. It is required that you wear prescription glasses or safety glasses at all times in the

Laboratory for your own protection. Contact lenses are particularly dangerous and they must not be worn in the laboratory.

Always read the label twice before taking any chemical from a bottle. If you are not sure if you have the right chemical, ask!

Unauthorized experiments are prohibited. Never taste chemicals or solutions. For using a solid, take it out on a piece of

paper. Never put anything on the palm of your hand. When diluting concentrated acid or base always add the concentrated acid or base

to water (never the reverse), while stirring the solution. Be very careful with sulfuric acid.

Do not waste chemicals and reagents. Use the minimum quantity necessary. Never remove a bottle from the side shelf to your seat. When you are ready to leave the laboratory, your bench area should be rinsed off

with a wet sponge and the water, gas and air valves shut off. Make a faithful and systematic record of all that you do, in the practical note-book.

Never record reading on scraps of paper.

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Contents

S.No. Name of Practical Page No.

1 To estimate the strength (in gm/L) of potassium permanganate solution by titrating against standard ferrous ammonium sulphate solution.

3

2

To estimate the strength in g/L of a given unknown solution of potassium dichromate (K2Cr2O7) by titrating it with ferrous ammonium sulphate (FAS) using diphenylamine as an internal indicator.

5

3

To estimate the strength in g/L of a given unknown solution of potassium dichromate (K2Cr2O7) by titrating it with ferrous ammonium sulphate (FAS) using potassium ferricyanide as an external indicator.

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4

To determine iodometrically the strength (in gm/L) of a given unknown potassium dichromate (K2Cr2O7) solution using KI as a source of iodine and sodium thiosulphate (hypo, Na2S2O3) as an intermediate solution.

10

5

To estimate the strength in gm/L of sodium carbonate and sodium hydroxide in the given mixed alkali solution by titrating against an intermediate hydrochloric acid using phenolphthalein and methyl orange as indicators.

12

6 To estimate the strength in gm/L of ferrous ammonium sulphate solution by titrating against an intermediate potassium permanganate solution.

14

7 To determine the strength (gm/L) of a given unknown CuSO4 solution iodometrically using potassium iodide as source of iodine and sodium thiosulphate as an intermidiate solution.

16

8 To estimate the amount of free chlorine in a given water sample. 18

9 To determine the percentage of iron in plain carbon steel. 21

10 Preparation of Urea formaldehyde resin. 23

11 Photochemical reduction of ferric oxalate in cyanotype blue printing 24

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Experiment No: 1

To estimate the strength (in gm/L) of potassium permanganate solution by titrating against standard ferrous ammonium sulphate solution. Prepare standard solution (N/40) of ferrous ammonium sulphate for the experiment

1. Apparatus and Reagents: Burette (25ml), Pipette (10ml), conical flask (100ml), ferrous ammonium sulphate (FAS), potassium permanganate, dilute sulphuric acid

2. Theory: Ferrous ammonium sulphate or Mohrs Salt Fe(SO4)2(NH4)26H2O is a stable double salt of ammonium sulphate and ferrous sulphate. Its active constituent is ferrous sulphate which is oxidized to ferric sulphate by KMnO4 is presence of dil.H2SO4 at room temperature.

Reduction: 2KMnO4 + 3H2SO4 K2SO4 + 2MnSO4 + 3H2O + 5[O]

Oxidation: 2FeSO4(NH4)2SO46H2O + H2SO4 + [O] Fe(SO4)3 + 2(NH4)2SO4 + 13H2O

2KMnO4 + 10[FeSO4(NH4)2SO4.6H2O] + 8H2SO4 5Fe2(SO4)3 + 10(NH4)2SO4 + K2SO4 + 2MnSO4 + 8H2O

The ionic reaction may be written as:

2MnO4 + 10 Fe+2 + 16H+ 2Mn+2 + 10Fe+3 + 8H2O

At the end point permanent light pink is developed in the solution

3. Procedure: Wash the apparatus with distilled water Prepare a standard N/40 solution of FAS by dissolving 0.98 grams of FAS in distilled water in

volumetric flask (100 ml) Rinse the burette with KMnO4 then the fill the burette with KMnO4 solution. Note down the burettes

initial readings Rinse the pipette with FAS solution, pipette out 10ml solution and transfer it to conical flask Add 10 ml of dilute H2SO4 into the FAS solution in conical flask Titrate FAS solution present in conical flask with the KMnO4 solution filled in burette, continue

addition of KMnO4 solution drop by drop till the color of the solution just change to permanent pink color indicates the end point. Note down the volume of KMnO4 used (burette reading)

Repeat the titration to get concordant reading

4. Observation: Table: Titration between standard FAS (N/40) and KMnO4 solution Sl. No.

Volume of FAS solution (ml) (V1)

Burette reading (ml) Concordant volume of KMnO4 solution consumed (ml) (V2)

Initial Final 1 10

5

2 10 3 10 4 10

5. Calculations:

To calculate the strength of KMnO4 solution

N1V1 = N2V2

N1 = N/40 V2 = (from Table) V1 = 10ml N2 =

Strength (gm/L) of unknown KMnO4 solution = Normality (N2) equivalent weight (31.6) 6. Result:

The strength of a given unknown KMnO4 solution = . gm/L

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Experiment No: 2 To estimate the strength in g/L of a given unknown solution of potassium dichromate (K2Cr2O7) by titrating it with ferrous ammonium sulphate (FAS) using diphenylamine as an internal indicator. The standard solution of K2Cr2O7 is of N/40. 1 Apparatus and Reagents: Burette (25ml), Pipette (10ml), conical flask (100ml), volumetric flask (100ml), standard solution (N/40) of K2Cr2O7, intermediate ferrous ammonium sulphate (FAS) solution, diphenylamine indicator, dilute sulphuric acid solution

2 Theory: The oxidising agent K2Cr2O7 in presence of dil. H2SO4 liberates three atoms of oxygen K2Cr2O7 + 4H2SO4 K2SO4 + Cr2(SO4)3 + 4H2O + 3[O] The liberated [O] oxidizes ferrous ion (Fe+2) to ferric ion (Fe+3) 2FeSO4. (NH4)2SO4.6H2O + H2SO4 + [O] Fe2(SO4)3 + 2(NH4)2SO4 + 13H2O

The complete reaction is

6[FeSO4.(NH4)2SO4.6H2O] + K2Cr2O7 + 7H2SO4 3Fe2(SO4)3 + K2SO4 + Cr2(SO4)3 + 6(NH4)2SO4 + 43H2O

6Fe2+ + Cr2O72 + 14H+ 6Fe3+ + 2Cr3+ + 7H2O The color exhibited by the diphenylamine changes from greenish to purple at the end point. Ferrous ion (Fe+2) is titrated with dichromate in sulphuric acid medium. The presence of considerable amount of sulphuric acid is necessary in order to reduce the concentration of ferric ion by forming a colorless soluble and stable complex. Otherwise the ferric ion, because of its tendency to oxidize the indicator, prevents a sharp end point. The addition of preventive solution (sulphuric acid) thus helps in getting a sharp color change of the indicator at the end point. (Appearance of violet color indicates the end point). 3 Procedure: Wash the apparatus with distilled water. Rinse the burette with K2Cr2O7 solution and fill the burette with K2Cr2O7 solution. Note down

the initial reading of burette. Rinse the pipette with FAS solution. With the help of pipette measure 10ml. FAS solution,

transfer it to conical flask. Add 10ml. of dil.H2SO4 into the FAS solution. Add 2-3 drops of indicator solution. Add K2Cr2O7 solution from burette into FAS solution with constant shaking and observe the

color change. The appearance of purple color indicates the end point. Note down the burette readings.

Repeat the titration till concordant reading obtained. Follow the titration procedure for the unknown solution and obtain the burette reading.

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Diphenylamine

3. Observation:

Table A. Titration between standard K2Cr2O7 solution and intermediate FAS solution

Sl. No.

Volume of FAS Solution (ml.)

Burette reading (ml) Volume of K2Cr2O7 Solution consumed (V1 ml.)

Initial Final

10 ml

Table B. Titration between intermediate FAS solution and unknown K2Cr2O7 solution

Sl. No.

Volume of FAS Solution (ml)

Burette reading (ml) Volume of K2Cr2O7 Solution consumed (V4 ml.)

Initial Final

10 ml

5. Calculations: A. To calculate the strength of intermediate FAS (From Table A) N1V1 = N2V2

N1 = Strength of K2Cr2O7 (N/40) V1 = Volume of K2Cr2O7

N2 = Strength of intermediate FAS V2 = Volume of intermediate FAS We have to determine N2 = . B. To calculate the strength of unknown K2Cr2O7 (From Table B) N3V3 = N4V4

N3 = Strength of intermediate FAS (=N2) V3 = Volume of intermediate FAS

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N4 = Strength of unknown K2Cr2O7 V4 = Volume of unknown K2Cr2O7 We have to determine N4 = . Strength in gm/L of unknown K2Cr2O7 = Normality (N4) equivalent weight (49.093)

6. Result: The strength of a given unknown K2Cr2O7 solution = ---------- g/L

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Experiment: 3 To estimate the strength in g/L of a given unknown solution of potassium dichromate (K2Cr2O7) by titrating it with ferrous ammonium sulphate (FAS) using potassium ferricyanide as an external indicator. The standard solution of K2Cr2O7 is of N/40 1 Apparatus and Reagents: Burette (25ml), pipette (10ml), conical flask (100ml), white glazed tile or white paper, glass rod, standard solution of ferrous ammonium sulphate (FAS), intermediate K2Cr2O7 solution, potassium ferricyanide solution (indicator), dilute sulphuric acid

2 Theory: The oxidising agent K2Cr2O7 in presence of dil. H2SO4 liberates three atoms of oxygen K2Cr2O7 + 4H2SO4 K2SO4 + Cr2(SO4)3 + 4H2O + 3[O] The liberated [O] oxidizes ferrous ion (Fe+2) to ferric ion (Fe+3) 2FeSO4. (NH4)2SO4.6H2O + H2SO4 + [O] Fe2(SO4)3 + 2(NH4)2SO4 + 13H2O The complete reaction is

6[FeSO4.(NH4)2SO4.6H2O] + K2Cr2O7 + 7H2SO4 3Fe2(SO4)3 + K2SO4 + Cr2(SO4)3 + 6(NH4)2SO4 + 43H2O

6Fe2+ + Cr2O72 + 14H+ + 6Fe3+ + 2Cr3+ + 7H2O Potassium ferricynide is used as an external indicator which gives a greenish blue colour with Fe+2 ions due to the formation of ferro-ferricynide. 3Fe3+ + 2[Fe(CN)6]3- Fe3[Fe(CN)6]2 (Prussian blue colour) At the end point no blue colour is produced as all the Fe2+ ions present in the solution have completely oxidized to Fe3+ ions. 3 Procedure: Wash the apparatus with distilled water. Rinse the burette with K2Cr2O7 solution and fill the burette with K2Cr2O7 solution. Note down

the initial reading of burette. Rinse the pipette with FAS solution. With the help of pipette measure 10ml. FAS solution,

transfer it to conical flask. Add 10ml. of dil.H2SO4 into the FAS solution. Take clean and dry porcelain plate (or white paper if porcelain plate is not available) and

arrange on it a number of tiny drops of the indicator in a row with help of a glass rod as shown below.

Add some amount of K2Cr2O7 from burette to FAS solution in conical flask. Now take a clean rod and dip it in the reaction mixture present in conical flask, touch it with

indicator drop on porcelain plate, appearance of blue color indicates that end point is yet to come.

Add some more amount of K2Cr2O7 and repeat the procedure with clean glass rod. If the intensity of prussion blue color has faded then K2Cr2O7 should be added drop wise and checking should be done after addition of every drop of K2Cr2O7 solution.

When color of indicator does not change then it shows the appearance of end point. Repeat the titration procedure till concordant readings are obtained.

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Follow the same procedure for the unknown solution, obtain the burette readings in similar manner.

4. Observation: Table A. Titration between standard K2Cr2O7 solution and intermediate FAS solution

Sl. No. Volume of FAS (ml.)

Volume of K2Cr2O7 added

Color of indicator Inference

1 10

1 10

1 10

Table B. Titration between intermediate FAS solution and unknown K2Cr2O7 solution

Sl. No. Volume of FAS (ml.)

Volume of K2Cr2O7 added

Color of indicator Inference

1 10

1 10

1 10

5 Calculations: A. To calculate the strength of intermediate FAS (From Table A) N1V1 = N2V2 N1 = Strength of K2Cr2O7 (N/40) V1 = Volume of K2Cr2O7

N2 = Strength of intermediate FAS V2 = Volume of intermediate FAS We have to determine N2 = . B. To calculate the strength of unknown K2Cr2O7 (From Table B) N3V3 = N4V4

N3 = Strength of intermediate FAS (=N2) V3 = Volume of intermediate FAS


6 Result: The strength of a given unknown K2Cr2O7 solution = ---------- g/L

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Experiment No: 4 To determine iodometrically the strength (in gm/L) of a given unknown potassium dichromate (K2Cr2O7) solution using KI as a source of iodine and sodium thiosulphate (hypo, Na2S2O3) as an intermediate solution; the standard solution potassium dichromate is of N/40 1 Apparatus and Reagents: Burette (25ml), Pipette (10ml), Conical Flask (100ml), Volumetric Flask (100ml), Measuring Cylinder (10ml), Sodium thiosuphate solution, potassium dichromate solution, potassium iodide solution, dilute sulphuric acid solution.

2 Theory: When potassium iodide is added to potassium dichromate it becomes brick red, an equivalent amount of iodine liberated. K2Cr2O7 + 7H2SO4 + 6KI K2SO4 + Cr2(SO4)3 + 7H2O + 3I2 The liberated iodine is titrated against standard sodium thiosulpate in presence of starch solution as an indicator. The blue color appears due to adsorption of iodine on starch. The iodine immediately reacts with sodium thiosuphate. When the end point reaches the blue color of iodine starch complex suddenly disappears and pure green solution appears due to Cr2(SO4)3. 2Na2S2O3 + I2 Na2S4O6 + 2NaI Sodium tetrathionate (colourless) 3 Procedure: (i) Wash the apparatus with distilled water. (ii) Rinse pipette with K2Cr2O7 solution (N/40) and transfer 10ml. of it to conical flask. (iii) Add 10ml. of dilute sulphuric acid to conical flask. (iv) Add 10ml. of KI solution, brick red color solution is obtained due to liberation of iodine. (v) Start adding sodium thiosulphate solution from burette, the brown color goes on fading as

the hypo solution is added. (vi) When only a faint yellow color remains, add 2-4 drops of starch solution, the solution

becomes dark blue. To avoid excess adsorption of iodine on the starch particle, which delays end point, indicator is added when solution is faint yellow.

(vii) Add more sodium thiosuphate from burette till appearance of light green color which indicates the end point. Note down the burette readings.

(viii) Repeat the procedure till 3 concordant readings. (ix) Same procedure is followed for the unknown solution of K2Cr2O7. Observation: Table A. Titration of standard K2Cr2O7 solution with intermediate Na2S2O3 solution

S.No. Vol. of K2Cr2O7 solution (ml)

Burette Reading Volume of Na2S2O3

consumed

Concordant reading

(V1)

Initial

Final 1 10 2 10 3 10

.

4 10

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Table B. Titration of unknown K2Cr2O7 solution with intermediate Na2S2O3 solution

S.No. Vol. of K2Cr2O7 solution (ml)

Burette Reading Volume of Na2S2O3

consumed

Concordant reading

(V4)

Initial

Final 1 10 2 10 3 10

.

4 10

4 Calculations: A. To calculate the strength of intermediate Na2S2O3 (From Table A) N1V1 = N2V2

N1 = Strength of K2Cr2O7 (N/40) V1 = Volume of K2Cr2O7

N2 = Strength of intermediate Na2S2O3 V2 = Volume of intermediate Na2S2O3 We have to determine N2 = . B. To calculate the strength of unknown K2Cr2O7 (From Table B) N3V3 = N4V4

N3 = Strength of intermediate Na2S2O3 (=N2) V3 = Volume of intermediate Na2S2O3


5 Result:

The strength of a given unknown K2Cr2O7 solution = ---------- g/L

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Experiment No: 5

To estimate the strength in gm/L of sodium carbonate and sodium hydroxide in the given mixed alkali solution by titrating against an intermediate hydrochloric acid using phenolphthalein and methyl orange as indicators. Use N/20 Na2CO3 as standard solution.

1 Apparatus and Reagents:

Burette (25 ml), pipette (10 ml), Mixed alkali (NaOH + Na2CO3) solution, HCl solution, phenolphthalein, methyl orange, sodium carbonate

2 Theory:

It is a double indicator titration method hence, different indicators are used at two different stages of the titration. In this titration when sodium carbonate and sodium hydroxide mixture solution is titrated with hydrochloric acid, the neutralization occurs in two stages. In the first stage, sodium hydroxide is completely neutralized while Na2CO3 partially neutralized. Phenolphthalein is used as an indicator.

NaOH + HCl NaCl + H2O Na2CO3 + HCl NaHCO3 + NaCl

At the first end point (P) the pink colour of phenolphthealein disappears with change of pH range 8.3 10.00 At this stage methyl orange indicator is added and the titration is continued. At the next end point (M) the yellow colour of the solution turns to pink in the pH range 3.1 4.4

Here reading (M) means total volume of HCl used , from the beginning of the experiment.

Na2CO3 + HCl NaHCO3 + NaCl NaHCO3 + HCl NaCl + H2O + CO2

3 Procedure:

(i) Wash the apparatus with distilled water. (ii) Rinse the burette with HCl solution. Then fill the burette with HCl solution, make sure there are no

air bubbles in the burette. Note down the burette reading. (iii) Rinse the pipette with mixed alkali solution. Transfer 10 ml. of mixed alkali solution to washed

conical flask. (iv) Add 2-3 drops of phenolphthalein indicator to mixed alkali solution in conical flask, a pink colour

appears. (v) Add HCl from burette solution drop wise with constant shaking, observe the colour change. The

disappearance of pink colour indicators the first end point [P]. (vi) Add 2-3 drops of methyl orange. Continue the titration with same solution in conical flask. (vii) Add more HCl from burette drop wise into mixed alkali solution and observe the colour change.

The change of colour from yellow to pink indicates the second end point. Note down the burette reading [M]

(viii) Repeat the titration procedure till concordant readings are obtained.

Table A. Titration between standard Na2CO3 solution and intermediate HCl solution

Sl. No. Vol. of Na2CO3 solution (ml)

Burette Reading Volume of HCl consumed

Concordant reading

(V2)

Initial

Final 1 10 2 10

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3 10 .

4 10 Table B. Titration between standard HCl solution and mixed alkali solution

Sl. No.

Vol. of mixed alkali

solution (ml)

Burette Reading Volume of HCl for Na2CO3

(=V4) 2(cb)

Volume of HCl for NaOH (=V4)

(ca) 2(cb) Initial

(a) First end point (b)

Second end point

(b)

1 10 2 10 3 10

.

4 10

4 Calculations:

A. To calculate the strength of intermediate HCl (From Table A) N1V1 = N2V2 N1 = Strength of Na2CO3 (N/20) V1 = Volume of Na2CO3

N2 = Strength of intermediate HCl V2 = Volume of intermediate HCl

We have to determine N2 = . B. To calculate the strength of Na2CO3 (From Table B) N3V3 = N4V4 N3 = Strength of Na2CO3 V3 = Volume of Na2CO3


We have to determine N3 = . Strength in gm/L of unknown Na2CO3 = Normality (N3) equivalent weight (52.99) C. To calculate the strength of NaOH (From Table B) N5V5 = N6V6 N5 = Strength of NaOH V5 = Volume of NaOH


We have to determine N5 = . Strength in gm/L of unknown NaOH = Normality (N5) equivalent weight (40.0) 5 Result: In the given alkali mixture,

The strength of Na2CO3 = ---------- g/L The strength of NaOH = ---------- g/L

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Experiment No: 6

To estimate the strength in gm/L of ferrous ammonium sulphate solution by titrating against an intermediate potassium permanganate solution; the strength of standard solution of ferrous ammonium sulphate is N/40

1 Apparatus and Reagents:

Burette (25ml), Pipette (10ml), conical flask (100ml), ferrous ammonium sulphate (FAS), potassium permanganate, dilute sulphuric acid

2 Theory:

Ferrous ammonium sulphate or Mohrs Salt Fe(SO4)2(NH4)26H2O is a stable double salt of ammonium sulphate and ferrous sulphate. Its active constituent is ferrous sulphate which is oxidized to ferric sulphate by KMnO4 is presence of dil.H2SO4 at room temperature.

2KMnO4 + 10[FeSO4(NH4)2SO4.6H2O] + 8H2SO4 5Fe2(SO4)3 + 10(NH4)2SO4 + K2SO4 + 2MnSO4 + 8H2O

The ionic reaction may be written as:

2MnO4 + 10 Fe+2 + 16H+ 2Mn+2 + 10Fe+3 + 8H2O

At the end point permanent light pink is developed in the solution

3. Procedure:

Wash the apparatus with distilled water Rinse the burette with KMnO4 then the fill the burette with KMnO4 solution. Note down the burettes

initial readings Rinse the pipette with FAS solution, pipette out 10ml.solution and transfer it to conical flask Add 10 ml. of dilute H2SO4 into the FAS solution in conical flask Titrate FAS solution present in conical flask with the intermediate KMnO4 solution filled in burette,

continue addition of KMnO4 solution drop by drop till the color of the solution just change to permanent pink color indicates the end point. Note down the volume of KMnO4 used (burette reading)

Repeat the titration to get concordant reading Carryout the titration of unknown FAS solution with standardized intermediate KMnO4 solution;

repeat the procedure as mentioned above

4. Observation:

Table A. Titration between standard FAS solution and intermediate KMnO4 solution Sl. No.



Initial Final 1 10

2 10

3 10

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Table B. Titration between unknown FAS solution and standardized intermediate KMnO4 solution

Sl. No.



Initial Final 1 10

2 10

3 10

4 10

5. Calculations:

To calculate the strength of intermediate KMnO4

N1V1 = N2V2

N1 = N/40 V2 = (from Table A) V1 = 10ml N2 =

To calculate strength of unknown FAS solution

N3V3 = N4V4 N3 = (=N2) V4 = (from Table B) V3 = 10ml N4 =

To calculate the strength in gm/L of unknown FAS Strength (gm/L) = Normality (N4) equivalent weight (392.14)

6. Result:

The strength of a given unknown FAS solution = . gm/L

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Experiment No: 7 To determine the strength (gm/L) of a given unknown CuSO4 solution iodometrically using potassium iodide as source of iodine and sodium thiosulphate as an intermidiate solution; N/40 CuSO4 solution is provided as a standard

1 Apparatus and Reagents: Burette (25 ml), pipette (10ml), conical flask (100 ml), Na2S2O3 solution, CuSO4 solution, KI solution

2 Theory: When KI is added to CuSO4 solution, an equivalent amount of iodine is liberated, and the solution becomes brown (due to liberation of I2) 2 CuSO4 + 4 KI 2K2SO4 + Cu2I2 + I2 The liberated iodine is titrated with standard solution of sodium thiosulphate by using starch as an indicator. I2 + 2 Na2S2O3 Na2S4O6 + 2NaI

The liberated I2 adsorbs on starch and gives deep blue or violet color in the solution

3 Procedure:

Wash the all the glass apparatus with distilled water

Rinse and fill the burette with Na2S2O3 solution Rinse the pipette with CuSO4 solution and take 10 ml of standard (N/40) CuSO4 solution in the

conical flask with the help of pipette.

Add 10 ml of KI solution to the CuSO4 solution in conical flask. The solution becomes brown Start titration immediately with Na2S2O3 solution till the color changes to pale yellow Add 2-3 drops starch as indicator, solution becomes blue or violet due to adsorption of iodine

on starch

Add more Na2S2O3 solution from burette till the blue/violet color disappears. The appearance of the milky white color indicates the presence of end point. Nome down the burette reading

There is sometimes tendency for the blue color to return due to liberation of adsorption of iodine on starch from cuprous iodide

So that the first complete disappearance of blue color is taken as the end point Repeat the procedure till you get consecutively three same readings (concordant readings) Estimate the strength of intermediate Na2S2O3 solution

Repeat the same procedure for the unknown CuSO4 solution and obtain concordant burette readings

Estimate the strength of unknown CuSO4 solution

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4 Observation:

Table A. Titration between standard CuSO4 solution (N/40) and intermediate Na2S2O3 solution Sl. No.

Volume of CuSO4 solution (ml) (V1)

Burette reading (ml) Concordant volume of Na2S2O3 solution consumed (ml) (V2)

Initial Final 1 10

2 10

3 10

4 10

Table B. Titration between unknown CuSO4 solution and standardized intermediate Na2S2O3 solution

Sl. No.

Volume of CuSO4 solution (ml) (V4)

Burette reading (ml) Concordant volume of Na2S2O3 solution consumed (ml) (V3)

Initial Final 1 10

2 10

3 10

4 10

5 Calculations:

To calculate the strength of intermediate Na2S2O3 N1V1 = N2V2

N1 = N/40 (Strength of CuSO4) V2 = (from Table A) V1 = 10ml N2 = (Strength of intermediate Na2S2O3)

To calculate strength of unknown CuSO4 solution

N3V3 = N4V4 N3 = (=N2; Strength of intermediate Na2S2O3) V3 = (from Table B)

V4 = 10ml N4 = (Strength of unknown CuSO4 solution)

To calculate the strength in gm/L of unknown CuSO4 solution (gm/L) = Normality (N4) equivalent weight (249.7)

6 Result:

The strength of a given unknown CuSO4 solution = . gm/L

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Experiment No: 8

To estimate the amount of free chlorine in a given water sample.

1 Apparatus and Reagents: Burette (25 ml), pipette (10ml), conical flask (100 ml), Na2S2O3 solution, CuSO4 solution, KI solution

2 Theory: Sterlised water is used for drinking purpose, usually chlorine gas is used for complete

removal of bacteria, fungicides and other micro-organism. The germicide action of Cl2 gas depends upon its reaction with water producing hypochlorus acid (HOCl) and nascent oxygen (O) both of which are powerful germicides.

If chlorine in water is beyond a certain limit it will make municipal water unfit for drinking purpose because chlorine gas is injurious to human metabolism. It is therefore, necessary to determine the amount in municipal water to adjust its quantities prior to the use of water for domestic drinking purposes. The analysis is based on the oxidation of potassium iodide (KI) by the free chlorine present in water. The liberated iodide is estimated by titrating against standard hypo solution, using starch as an indicator.

3 Procedure:

Wash the all apparatus with distilled water. Standardize the intermediate hypo solution by N/50 standard solution of K2Cr2O7. Rinse the burette with hypo solution and fill with standardized hypo solution. Note down

the initial reading of burette. Take 50ml. of given water sample in conical flask then add glacial acetic acid to maintain

3-4 PH, shake the solution and add 10ml of KI solution. Titrate the water sample with standardized hypo solution, add hypo solution from burette

till the solution in conical flask becomes faint yellow. Now add few drops of freshly prepared starch indicator, a blue colour appears. Continue to add solution drop wise with constant shaking till the blue colour disappeares,

it indicates the end point. Note down the burette reading. Repeat the titration till the concordant reading obtained.

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4 Observation:

Data for standard solution of K2Cr2O7 i) Equivalent Weight of K2Cr2O7 = 49.03

ii) Weight of watch glass = 16.6226gm iii) weight (ii)+ K2Cr2O7 = 16.6226gm. iv) Weight of K2Cr2O7 =(iii) - (ii) = 0.098gm v) Volume of K2Cr2O7 Solution = 100ml.

Table A. Titration between K2Cr2O7 and hypo solution. Sl. No.

Volume of K2Cr2O7 solution (ml)

Burette reading (ml) Volume of hypo used (ml)

Initial Final 1 10

2 10

3 10

4 10 Table B. Titration between water sample and hypo solution

Sl. No.

Volume of Water Sample (ml)

Burette reading (ml) Volume of hypo used (ml)

Initial Final 1 10

2 10

3 10

4 10

5 Calculations:

A. Normality of standard of K2Cr2O7 solution. = 1000 x Wt. of K2Cr2O7 100 x Eq.Wt. of K2Cr2O7 = 1000 x 0.098 100 x 49.03

= N 50

B. Strength of sodium thiosulphate solution. 9.5 ml of thio solution = 10ml. of N/50 K2Cr2O7 solution. Normality = 10 x N 9.5 x 50

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= 0.021N

C. Amount of Free Chlorine 50ml.of water sample = 2.0ml of 0.021 N hypo solution Normality = 2 x 0.021 50 Strength = 2 x 0.021 x 35.5 50 = 0.0298 x 106 ppm 103 = 29.8ppm

6 Result:

The strength of a given Free chlorine in water = . gm/L

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Experiment No: 9 To determine the percentage of iron in plain carbon steel

1 Apparatus and Reagents: Burette (25ml),pipette(10ml) conical flask (100ml) ,volumetric flask (100)ml, measuring cylinder. Potassium permanganate , FAS ( N/40), dilute sulphuric acid, plain carbon steel sample. 2 Theory: Plain carbon steel is an alloy of iron and carbon. The steel is classified into various categories suitable for different uses on the basis of carbon contents. The physical and chemical properties of steel are usually governed by content of iron and carbon. To determine the iron in steel , the steel is dissolved in dilute sulphuric acid and iron is converted in corresponding sulphate with the liberation of hydrogen gas.

The amount of iron (as Fe+3) can be estimated by titrating the solution against the standardised KMnO4 solution. The KMnO4 in the presence of dilute H2SO4 liberated free oxygen witch oxdises the Fe+2 to Fe+3 ion and the KMnO4 is reduced to managanous sulphate giving a colourless solution. At the end point, a slight excess of KMnO4 will impart its own characteristics pink colour.

3 Procedure:

Preparation of a solution of plain carbon steel: Weigh 0.2 gm. Of steel sample on a watch glass, transfer it to a beaker (100ml). Add about 40-50 ml. of sulphuric acid and heat gently. The steel goes into solution with a brisk evolution of hydrogen gas, to avoid loss of solution, cover the beaker with watch glass. When steel is dissolved completely, add granulated zinc (Zn). The zinc reacts with H2SO4 to give hydrogen gas, which prevents the oxidation of ferrous ions and also reduces the ferric (Fe+3) ions present, if any, Transfer the solution to 100ml. volumetric flask. Wash the beaker 2-3 times with distilled water and shake the solution thoroughly.

Standardise the H2SO4 solution as usual. Wash the apparatus with distilled water. Rinse the burette with standardized KMnO4 solution and fill the burette with it. Make

sure, there is no air bubbles in burette. Note down the initial reading of burette. Rinse the pipette with steel solution prepared as described above. Measure 10 ml solution

of plain carbon steel, transfer it to conical flask. Add about 10ml. of dil H2SO4 into plan carbon steel solution in conical flask . Titrate plan carbon steel solution present in conical flask with the N/40 KMnO4 solution

filled in burette continue addition of KMnO4 solution drop by drop till the colour of solution just change to permanent pink witch indicates the end point. Note down burette reading.

Repeat the titration procedure till the concordant reading obtained.

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4 Observation:

Table A. Titration of standard FAS solution with intermediate KMnO4 Sl. No.

Volume of FAS (ml) Burette reading (ml) Volume of KMnO4 solution consumed(ml)

Initial Final 1 10

2 10

3 10

4 10

Table B. Titration between plain carbon steel solution with standard KMnO4 solution

Sl. No.

Volume of plain carbon steel solution (ml)

Burette reading (ml) Volume of KMnO4 solution consumed(ml)

Initial Final 1 10

2 10

3 10

4 10

5 Calculations:

N1V1 = N2V2 N1 = Normality of plain carbon steel solution = ? V1 = Volume taken of plain carbon steel solution = 10ml. N2 = Normality of KMnO4 = N/40 V2 = Volume of KMnO4 solution consumed =

N1 =

N2V2V1

But Strength (in g/l) = Normality x Eq.Wt. 1000ml. of iron solution = Strength (in g/l) 100ml of iron solution contain = 0.2 gm of iron solution contain = -----------of iron 100gm of plain carbon steel contains = -------

6 Result:

The percentage of iron in steel = . gm/L

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Experiment No: 10 Preparation of Urea formaldehyde resin

1 Apparatus and Reagents: Beaker(250ml.), Measuring cylinder (25ml.),Stirring rod, formaldehyde(40%),urea, H2SO4(conc.) distilled water.

2 Theory: The urea formaldehyde resin is produced by condensation polymerization, reaction of urea with aqueous formaldehyde. Such resin is commercially important, it is used in packaging, water tumbles, unbreakable dishes, buttons, clock cases etc. Urea formaldehyde resins is water soluble and hence, are used as sizing agents and textile finishing resin. It is also used in the paper industry to improve the wet strength of paper. These also used as insulators.

+HCHO

Basic Medium

N CH2 N CH2 N CH2

CO

N CH2 N CH2 N CH2

Urea-formaldehyde resin (Cross-linked polymer)

UREA

CO

H2N

H2NCOCO

3 Procedure:

Take 25ml. of 40% formaldehyde solution in 250ml. beaker. Then add 10grms of urea in to the beaker. Stir the solution constantly until a saturated solution is obtained. Add few drops of H2SO4(Conc.) stir cautiously during the addition. At once voluminous white solid mass appears in the beaker. When the reaction is complete, wash the residue with water and dry the products formed and weight the urea formaldehyde resin formed.

4. Precautions: It is a vigorous reaction. Add HCl slowly and carefully

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Experiment No: 11

Photochemical reduction of ferric oxalate in cyanotype blue printing

1 Apparatus and Reagents: The solution required for this experiment are as follows:

1. 0.5 M oxalic acid 2. 0.67 M ferric chloride 3. 0.1 M HCL 4. 0.1 M potassium ferricyanide 5. 3.5 M diammonium phosphate 6. 0.03 M Potassium dichromate 7. Pair of glass plates 8. Whatmen filter paper

2 Theory: Cyanotype chemistry relies on two distinct reactions: ferric ions in a few organic-iron complexes

such as ammonium ferric citrate and ammonium ferric oxalate are reduced by light. The ferrous ions formed in this reaction in turn are made to react with potassium ferricyanide to form an insobule blue compound called Turnbulls blue. It is said that when you add ferric ions to ferrocyanide you get Prussian blue, a commonly used pigment in artist paints and when you add ferrous ions to ferricyanide you get Turnbulls blue. From the chemists viewpoint, Turnbulls blue is actually the same as Prussian blue, the different between the two, if any, are in the mode of addition of the ions and that in the original turnbulls blue, the passion of the ferrous and ferric ions in the lattice of cyanide ions are reversed from their positions in Prussian blue. However, the ferrous ions in Turnbulls blue are immediately oxidized by the neighboring ferric ions, which are themselves reduced to ferrous ions. The net result is that Prussian blue, Fe4[Fe(CN6)]3.15H2O, is formed. It has been shown from structural studies that the ironcyanide framework is the same in Prussian blue and Turnbulls blue prepared from different starting materials. The chemical equations for the reaction involved in blueprinting with ferric oxalate are as fellows. Under UV-light, ferric oxalate with the release of CO2. Ferrous oxalate dehydrate, a stable species is one of the possible in such a reaction.

Ferric ferrous The ferrous iron formed reacts with potassium ferricyanide to form ferroferricyanide (Prussian blue)

Some artists call as soluble Prussian blue and as insoluble Prussian blue. As can from the above equation, they are just different forms of the same substance and all form of Prussian blue are insoluble in water but can be dispersed as a fine colloidal blue suspension in water. Traditionally, ammonuium iron citrate was used for cyanotype printing but ammonium iron oxalate has better light sensivity, better penetration on paper and is not attacked by mould. In this experiment diammonium phosphate is added to reduce the sensitivity of the ferric oxalate reaction to light so that the sensitized paper may be prepare under diffuse laboratory light which would otherwise needs to be done in a darkroom.

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One also uses a very dilute solution of potassium dichromate to wash the finished print as dichromate is a well-known contrasting agent in photography which improves the sharpness of the image. It also help to oxidize and remove unreacted material.

After the paper is prepared and dried, a film negative or an object whose silhouette is to be printed is placed on the paper and the uncovered portion is exposed to sunlight or another brilliant source of light. Afterwards, the paper is treated with potassium ferricyanide solution and the excess ferric oxalate is washed from the paper. The unexposed and partly exposed part will have or less amount of ferrous iron and so the blue formed there will be less. 3 Procedure:

1. Pour 100 ml of 0.5 M oxalic acid into a 400 ml beaker and add 20 ml of the 3.5 M diammonium phosphate solution and mix well.

2. Place the beaker in your locker or any place, which has subdued light, and add 100 ml of the ferric chloride solution while stirring.

3. If a precipitate is formed, further stirring should dissolve it. Shut the locker and open it only when required, as the light sensitive ferric oxalate is ready to react.

4. Immerse four piece of bond paper of size 4 X 2.5 in the freshly prepared sensitizing solution. Cutting the paper into a semicircle and sliding it into the beaker may do this. Rotate the beaker and make sure that the paper is thoroughly wet.

5. Remove the wet piece of paper and place them between sheets of filter paper. (Make sure that the paper which touches the sheet does not have any reducing agents.) This should be done as quickly as possible and in a partially closed locker.

6. The length of time required for drying varies according to the type of print one wants to make. For opaque objects whose silhouettes are to be made, dry it for 10-15 minutes. If the paper is not dried long enough, the edges of the shadows will appear fuzzy. For making print from photonegatives, the paper must be dried completely. Moist paper can otherwise affect the gelation on the negative.

7. After the paper has dried, remove it from the filter paper sheets, place the opaque object on the top of the sensitized paper, compress it between sheets of glass and expose to sunlight.

The time required for exposure of a normal print in bright sunlight is about 4-5 minutes. During printing do not hold the glass plates, but lay them on the desk, windowsill or any flat surface. 8. After the exposure, smoothly dip the paper into 100 ml of 0.1 M ferricynanide solution kept

in a wide-mouthed dish. This as well as the following operations can be carried out in diffuse light on top of a desk. It is important that the paper is immersed all at once, otherwise lines will appear on the blue field of the print.

9. Remove the paper and dip it in 100 ml of the 0.03 M potassium dichromate solution for a minute. Afterwards, was the paper first in 0.1 M HCL and then tap water.

Make a series of 3-4 exposures, varying the time of optimize the best conditions. Use these conditions to obtain the most satisfactory pictures later.

ss practical

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