jee main chemistry important questions | Purification And Characterization Of Organic Compounds

Q 1 :
In Kjeldahl’s method for estimation of nitrogen, ${CuSO}_{4}$ acts as: [2024]

reducing agent
catalytic agent
hydrolysis agent
oxidizing agent

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(B)

In Kjeldahl’s method ${CuSO}_{4}$ acts as catalyst.

Q 2 :
Given below are two statements:

Statement (I): Kjeldahl method is applicable to estimate nitrogen in pyridine.

Statement (II): The nitrogen present in pyridine can easily be converted into ammonium sulphate in Kjeldahl method.

In the light of the above statements, choose the correct answer from the options given below: [2024]

Statement I is true but Statement II is false
Statement I is false but Statement II is true
Both Statement I and Statement II are true
Both Statement I and Statement II are false

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(D)

Kjeldahl method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in the ring (e.g. pyridine) as nitrogen of these compounds does not change to ammonium sulphate under these conditions.

Q 3 :
Following Kjeldahl's method, 1 g of organic compound released ammonia, that neutralised 10 mL of 2M $H_{2} {SO}_{4}$ . The percentage of nitrogen in the compound is ______%. [2024]

0%

(56)

$Millimoles of sulphuric acid (n_{H_{2} {SO}_{4}}) = Molarity \times volume in mL$

$= 2 M \times 10 mL = 20 mmol$

$Ammonia is a base, it reacts with sulphuric acid to form salt:$

$2 {NH}_{3} + H_{2} {SO}_{4} \to {({NH}_{4})}_{2} {SO}_{4}$

$By stoichiometry:$

$\frac{n_{N H_{3}}}{2} = \frac{n_{H_{2} S O_{4}}}{1}$

$\frac{n_{N H_{3}}}{2} = \frac{20 mmol}{1}$

$n_{N H_{3}} = 40 mmol = 0.04 mol$

$Moles of N (n_{N}) = Moles of ammonia (n_{N H_{3}}) = 0.04 mol$

$Since amount of nitrogen is conserved, number of moles of N in organic compound (n_{N}) = number of moles of N in ammonia$

$(n_{N H_{3}}) = 0.04 mol$

$Weight of N in organic compound (W_{N}) = n_{N} \times Molar mass of N$

$= 0.04 mol \times 14 {g mol}^{- 1} = 0.56 g$

$Percentage of nitrogen in organic compound:$

$= \frac{W_{N}}{W_{compound}} \times 100 = \frac{0.56}{1} \times 100 = 56 %$

Topic Question Set

Q 1 :
In Kjeldahl’s method for estimation of nitrogen, ${CuSO}_{4}$ acts as: [2024]

Q 3 :
Following Kjeldahl's method, 1 g of organic compound released ammonia, that neutralised 10 mL of 2M $H_{2} {SO}_{4}$ . The percentage of nitrogen in the compound is ______%. [2024]

0%

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Topic Question Set

Q 1 : In Kjeldahl’s method for estimation of nitrogen, CuSO4 acts as: [2024]

Q 3 : Following Kjeldahl's method, 1 g of organic compound released ammonia, that neutralised 10 mL of 2M H2SO4. The percentage of nitrogen in the compound is ______%. [2024]

0%

Want Us to Email you About Special Offers & Updates?

Q 1 :
In Kjeldahl’s method for estimation of nitrogen, ${CuSO}_{4}$ acts as: [2024]

Q 3 :
Following Kjeldahl's method, 1 g of organic compound released ammonia, that neutralised 10 mL of 2M $H_{2} {SO}_{4}$ . The percentage of nitrogen in the compound is ______%. [2024]