LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 17

FIRST SEMESTER – NOV 2006

CH 1809 – ANALYTICAL CHEMISTRY

 

 

Date & Time : 02-11-2006/1.00-4.00   Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

Answer ALL the questions                                                                            (10 ´ 2 = 20 marks)

 

1. A Chemical balance is used to weigh 2.0000g of FAS.  Find out the maximum relative uncertainty associated with the weight in ppt.
2. Determine the pH of the mixture containing 20.00 mL of 0.0750 m CH₃COOH and
   30.00 mL of 0.0500 M NaOH.  K_a of CH₃COOH is 1 x 10^-5.
3. How does GSC differ from GLC?
4. Mention the factors which affect pm at the equivalence point.
5. How does AAS differ from Flame photometry?
6. Explain why MgCo₃ is thermally less stable compared to Na₂CO₃.
7. What is the difference between DTA and DSC.
8. What will be the mass of ion deposited by a current of 9.65 A in 2 minutes passed in to a solution of ferric chloride(Fe : At . wt = 55.85)?
9. How many faraday current is required to reduce one mole of MnO₄ to mn²⁺.
10. State Beer Lambert’s Law.

 

PART – B

Answer any EIGHT questions                                                                       (8 ´ 5 = 40 marks)

 

1. Apply ‘t’ test and ‘F’ test to check whether two sets of data differ significantly or not.
2. Discuss the principle of GLC.
3. Draw the titration curves for the following and interpret the result.

• 00 mL of 10^-1M CH₃ COOH vs 10^-1M NaOH
• 00 mL of 10^-2 M CH₃ COOH vs 10^-2 M NaOH

1. Show that the fraction of completely ionized form of EDTA depends on pH.
2. A solution containing 8.75 ppm KmnO₄ has a transmittance of 75% in a  1 cm cell at
   520 nm.  Calculate the molar absorptivity of KmnO₄.
3. The organic matter in a 0.3775 g sample of a mercuric ointment is decomposed with HNO₃ .  After dilution the Hg⁺² is titrated with 21.30 mL of a 0.1140 M solution of NH₄SCN.  Calculate the % of Hg (f.w = 200.59) in the ointment and express it scientifically                 Hg⁺² + 2SCN⇌  Hg(SCN)₂ .
4. Cupric nitrate decomposes as follows.

Cu (NO₃)₂ .2½ H₂O  Cu (NO₃)₂ + 2½ H₂O (100-150^oC)

Cu(NO₃)₂   CuO + NO₂ + 1½ O₂ (200 – 280^oC)

Calculate the residual mass if 100 mg of hydrated cupric nitrate in heated upto 250^oC.

1. Calcium oxalate monohydrate undergoes three types of weight loss, whereas magnesium oxalate shows only two types of weight loss.  Explain.
2. How will you estimate copper electro gravimetrically?
3. Calculate the emf w.r.f  SCE when 1 ml of 0.25 m K₂Cr₂O₇ is added to 20 ml of 0.05 m Fe²⁺ in 0.1 m HCl.
4. Explain the coulometric titration of I^–   Vs   S₂O₃ ^2–
5. Explain the quantitative application of polorography.

 

PART – C

Answer any FOUR questions                                                            (4 ´ 10 = 40 marks)

 

1. Potassium can be determined by flame emission spectrometry using a lithium internal standard.  The following data were obtained for standard solutions of KCl and an unknown containing a constant known amount of LiCl as internal standard.  All the intensities were corrected for background by subtracting the intensity of a blank.

Conc K, ppm	Intensity of Emission
1.0	10.0
2.0	15.3
5.0	34.7
7.5	65.2
10.0	95.8
Unknown	47.3

 

Apply the method of least squares to obtain the equation for the best straight line through these points.  Determine the standard deviation of the slope and the result, if the unknown intensity corresponds to the mean of 4 measurements.  Also find out the concentration of K in the unknown.

1. Draw the flow sheet diagram of HPLC and explain the function of the components.
2. a) A 0.4085 g sample containing pb, mg and Zn was dissolved and treated with cyanide     to complex and mask the zinc;

Zn⁺² + 4 CN^–   [Zn(CN)₄] ^2–.

Titration of the lead and magnesium required 42.20 ML of 0.02065 M EDTA.  The lead was next masked with BAL (2,3 dimercaptophepanol), and the released EDTA was titrated with 19.35 mL of 0.007650 m Mg⁺² solution.  Finally HCHO was introduced to demask the Zinc;
[Zn(CN)₄] ^2– + 4HCHO + 4H₂O Zn⁺² + 2OH^– + 4 CNCH₂OH.
The zinc was then titrated with 28.60 mL of 0.02065 EDTA.  Calculate the percentages of the three metals in the sample.                                                         (7)

1. b) Explain the principle of Flame Photometry. (3)

1. a) How will you prove the liberation of Carbon monoxide by thermal analysis.

2. b) 2.92 mg of a sample of mgSo₄.7H₂O losses 0.62 mg at 105^o C due to the following

reaction
MgSo₄.7 H₂O   MgSO₄.H₂O + 6H₂O.

calculate the % purity of the sample.

1. Explain the potentimetric titration of acidified Fe²⁺ against standard MnO₄^–

[SRP: Fe³⁺, Fe²⁺ = 0.77       MnO₄^–, Mn²⁺, H⁺ = 1.51 V]

Write the electrode  reactions before and after the equivalence point and draw the titration   curve.

1. a) Explain the instrumentation of a classical fluorimeter.

1. b) Explain the applications of Cyclic voltametry.

 

 

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