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0.303 g of an organic compound was analy...

0.303 g of an organic compound was analysed for nitrogen by Kjeldahl's method. The ammonia evolved was absorbed in 50 ml of 0.1 N `H_2 SO_4`. The excess acid required 25 ml of 0.1 N NaOH for neutralisation. Calculate the percentage of nitrogen in the compound.

A

8

B

16

C

20

D

25

Text Solution

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The correct Answer is:
A, C
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An organic compound contains 69.4% carbon and 5.8% hydrogen. A sample of 0.303 g of this compound was analysed for nitrogen by Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.05 M H_2 SO_4 . The excess acid required 25 mL of 0.1 M NaOH for neutralisation. Determine the molecular formula of the compound, if its molecular mass is 121.

A sample of 0.50 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H_(2)SO_(4) . The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. What would be the percentage composition of nitrogen in the compound?

Estimation of nitrogen: There are two methods for the estimation of nitrogen (i) Dumas method and (ii) Kjedahl's method. i. Dumas method: A known mass of compound is heated with copper oxide (CuO) in an atomsphere 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 (N_(2)) + (2x + y//2) CU The gaseous mixture is passed over a heated copper gauze which converts traces of nitrogen oxides formed to N_(2) . The gaeous mixture is collected over an aqueous solution of KOH which absorbs CO_(2) , and nitrogen is callected in the upper part of the graduated tube. ii. 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) (25ml), 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 passed 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 amount of acid used against NH_(3) can be thus be known and from this the percentage of nitrogen 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) (iii) This method is not applicable to compounds containing N in intro and azo groups, and N present in the ring (e.g., pyridine) as N of these compounds does not change to (NH_(4))_(2)SO_(4) (ammonium sulphate) under these reaction conditions 0.50 gm of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50ml of 0,5M H_(2)SO_(4) . The residual acid required 60 ml of M/2 NaOH solution. Find the percentage of nitrogen in the compound

0.50 gm of an organic compound was treated according to Kjeldahl's meghod. The ammonia evolved was absorbed in 50 ml of 0.5 MH_2SO_4 . The residual acid required 60 ml of (M)/(2)NaOH solution. Find the percentage of nitrogen in the compound.

0.35 g of an organic susbtance was Kjeldahilsed and the ammonia obtained was passed into 100ml of M/ 10H_(2)SO_(4) The excess acid required 154 ml of M//10 NaOH for neurtralisation, calculate the % of nitrogen in the compound.

For the estimation of nitrogen, 1.4 g of an organic compound was digested by Kjeldahl's method and the evolved ammonia was absorbed in 60 mL of M//10 sulphuric acid. The unreacted acid required 20 mL of M//10 sodium hydroxide for complete neutralisation. The percentage of nitrogen in the compound is

0.255 of an organic nitrogenous compound was Kjeldahlised and the ammonia evolved was absorbed in 50cm^(3) of (N)/(10) H_(2)SO_(4) . The excess acid required 10cm^(3) of (N)/(5) NaOH. Calculate the percentage of nitrogen in the given compound

0.70 g of an organic compound was kjeldahlised and the ammonia obtained was passed into 150 ml of (M/5) H_2SO_4 . The excess acid required 100 ml of (M/5) NaOH for neutralisation, the percentage of nitrogen on the organic compound is

Estimation of nitrogen: There are two methods for the estimation of nitrogen (i) Dumas method and (ii) Kjedahl's method. i. Dumas method: A known mass of compound is heated with copper oxide (CuO) in an atomsphere 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 (N_(2)) + (2x + y//2) CU The gaseous mixture is passed over a heated copper gauze which converts traces of nitrogen oxides formed to N_(2) . The gaeous mixture is collected over an aqueous solution of KOH which absorbs CO_(2) , and nitrogen is callected in the upper part of the graduated tube. ii. 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) (25ml), 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 passed 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 amount of acid used against NH_(3) can be thus be known and from this the percentage of nitrogen 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) (iii) This method is not applicable to compounds containing N in intro and azo groups, and N present in the ring (e.g., pyridine) as N of these compounds does not change to (NH_(4))_(2)SO_(4) (ammonium sulphate) under these reaction conditions 0.4gm of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50ml of 0.5M H_(3)PO_(3) . The residual acid required 30 ml of 0.5M Ca(OH)_(2) . Find the percentage of N_(2) in the compound

29.5 mg of an organic compound containing nitrogen was digested according to Kjeldahl's method and the evolved ammonia was absorbed in 20 mL of 0.1 M HCl solution. The excess of the acid required 15 mL of 0.1 M NaOH solution for complete neutralization. The percentage of nitrogen in the compounds is

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