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(a) Suggest a quantitative method for es...

(a) Suggest a quantitative method for estimation of a gas which protects us from U.V. rays of the sun.
(b) Nitrogen oxides emitted from the exhaust system of supersoni jet aeroplanes slowly deplete the concentration of ozone layer in upper atmosphere. Comment.

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(a) Ozone `(O_(3))` absorbs ultraviolet radiations (220 - 290 nm) and thus protects us from the harmful radiations of the sun.
(b) NO present in the exhaust of supersonic aeroplanes combines rapidly with `O_(3)` forming `O_(2)` thereby depleting the concentration of `O_(3)` in the upper atmosphere.
`NO(g) + O_(3)(g) rarr NO_(2)(g) + O_(2)(g)`
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Estimation of Nitrogen: There are two methods for the estimation of nitrogen (1) Dumas method and (2) Kjedahl's method. (1) Duma's method: A known mass of compound is heated with copper oxide (CuO) in an atmosphere of CO_(2) , which gives free nitrogen along with CO_(2) and H_(2)O . C_(x)H_(y)N_(z)+(2x+(y)/(2))CuO rarr xCO_(2) +(y)/(2)(H_(2)O)+(z)/(2)+(2x+(y)/(2))Cu. The gaseous mixture is passed over a heated copper gauze which converts traces of nitrogen oxides formed of N_(2) .The gaseous mixture is collected over an aqueous solution of KOH which absorbs CO_(2) and nitrogen is collected in the upper part of the graduated tube. (2) kjeldahl's method: A known mass of organic compound (0.5 gm) is mixed with K_(2)SO_(4) (10 gm) and CuSO_(4) (1.0 gm) or a drop of mercury (Hg) and conc. H_(2)SO_(4) (25 ml) , and heated in Kjeldahl's flask. CuSO_(4) or Hg acts as a catalyst , while K_(2)SO_(4) raises the boiling point of H_(2)SO_(4) . The nitrogen in the organic compound is quantitatively converted to ammonium sulphate . The resulting mixture is then distilled with excess of NaOH solution and the NH_(3) evolved is passes into a known but excess volume of standard HCl or H_(2)SO_(4) . The acid left unused is estimated by titration with some standard alkali . The amound of acid used against NH_(3) can thus be known and from this the percentage of nitogen is calculated. (a) C+H +S underset(H_(2)SO_(4))overset("conc.")rarr CO_(2) + H_(2)O +SO_(2) (b) N underset(H_(2)SO_(4))overset("conc.")rarr (NH_(4))_(2)SO_(4) (c) (NH_(4))_(2)SO_(4)+2NaOH rarr Na_(2)SO_(4)+2NH_(3) + 2H_(2)O (d) 2NH_(3) + H_(2)SO_(4) rarr (NH_(4))_(2)SO_(4) (3) This method is not applicable to compounds containing N in nitro and azo groups,and N persent in the ring (e.g., pyridine as N of these conpounds does not change to (NH_(4))_(2)SO_(4) (ammonium sulphate ) under these reaction condition. 0.30 gm of an organic compound gave 50 ml of nitrogen collected at 300K and 715 mm pressure in water or Duma's method . Calculate the percentage of nitrogen in the compound . (Vapour pressure of aqueous tension of water at 300k is 15 mm)

Estimation of Nitrogen: There are two methods for the estimation of nitrogen (1) Dumas method and (2) Kjedahl's method. (1) Duma's method: A known mass of compound is heated with copper oxide (CuO) in an atmosphere of CO_(2) , which gives free nitrogen along with CO_(2) and H_(2)O . C_(x)H_(y)N_(z)+(2x+(y)/(2))CuO rarr xCO_(2) +(y)/(2)(H_(2)O)+(z)/(2)+(2x+(y)/(2))Cu. The gaseous mixture is passed over a heated copper gauze which converts traces of nitrogen oxides formed of N_(2) .The gaseous mixture is collected over an aqueous solution of KOH which absorbs CO_(2) and nitrogen is collected in the upper part of the graduated tube. (2) kjeldahl's method: A known mass of organic compound (0.5 gm) is mixed with K_(2)SO_(4) (10 gm) and CuSO_(4) (1.0 gm) or a drop of mercury (Hg) and conc. H_(2)SO_(4) (25 ml) , and heated in Kjeldahl's flask. CuSO_(4) or Hg acts as a catalyst , while K_(2)SO_(4) raises the boiling point of H_(2)SO_(4) . The nitrogen in the organic compound is quantitatively converted to ammonium sulphate . The resulting mixture is then distilled with excess of NaOH solution and the NH_(3) evolved is passes into a known but excess volume of standard HCl or H_(2)SO_(4) . The acid left unused is estimated by titration with some standard alkali . The amound of acid used against NH_(3) can thus be known and from this the percentage of nitogen is calculated. (a) C+H +S underset(H_(2)SO_(4))overset("conc.")rarr CO_(2) + H_(2)O +SO_(2) (b) N underset(H_(2)SO_(4))overset("conc.")rarr (NH_(4))_(2)SO_(4) (c) (NH_(4))_(2)SO_(4)+2NaOH rarr Na_(2)SO_(4)+2NH_(3) + 2H_(2)O (d) 2NH_(3) + H_(2)SO_(4) rarr (NH_(4))_(2)SO_(4) (3) This method is not applicable to compounds containing N in nitro and azo groups,and N persent in the ring (e.g., pyridine as N of these conpounds does not change to (NH_(4))_(2)SO_(4) (ammonium sulphate ) under these reaction condition. 0.50 gm of an organic compound was treated according to Kjedahl's method . The ammonia evolved was absorbed in 50 ml of (M)/(2) NaOH solution. Find the percentage of nitrogen in the compound.

PRADEEP-P-BLOCK ELEMENTS -CONCEPTUAL QUESTION
  1. All the bonds in SF(4) are not equivalent. Why ?

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  2. Sulphur hexafluoride is used as a gaseous electrical insulator.

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  3. (a) Suggest a quantitative method for estimation of a gas which protec...

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  4. Sulphur disappears when boiled with an aqueous solution of sodium sulp...

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  5. Draw the structure of : SO(3)^(2-)

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  6. Give a chemical reaction in the support of the observation that sulphu...

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  7. Electron gain enthalpies of halogens are largely negative. Explain.

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  8. The negative value of electron gain enthalpy is less for fluorine than...

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  9. F2 has lower bond dissociation enthalpy than Cl2. Why?

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  10. I(2) is more soluble in KI than in water. Why ?

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  11. Why fluorine does not exhibit any positive oxidation state?

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  12. Fluoride ion has higher hydration enthalpy than chloride ion. Give rea...

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  13. Among halogens, F(2) is the strongest oxidising agent. Or F(2) is a ...

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  14. F(2) is a stronger oxidising agent than Cl(2)

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  15. Addition of Cl(2) to KI solution gives it a brown colour but excess of...

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  16. Give chemical reaction in support of the observation that iodide ions ...

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  17. Arrange the following in the decreasing order of their boiling points ...

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  18. (i) Hydrogen fluoride is a weaker acid than hydrogen chloride in aqueo...

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  19. Complete the following reaction equation : NaClO(3) (aq) + SO(2)(g) ra...

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  20. More metal fluorides are ionic in nature than metal chlorides. Assign ...

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