NCERT Solutions

Derive the structure of (i) 2-Chlorohexane, (ii) Pent-4-en-2-ol, (iii) 3- Nitrocyclohexene, (iv) Cyclohex-2-en-1-ol, (v) 6-Hydroxyheptanal.

Giving justification, categorise the following molecules/ions as nucleophile or electrophile: $\mathrm{HS}^{-}, \mathrm{BF}_{3}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{O}^{-}, \left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}:, \mathrm{Cl}^{+}, \mathrm{CH}_{3}-\stackrel{+}{\mathrm{C}}=\mathrm{O}, \mathrm{H}_{2} \mathrm{N}:^{-}, \stackrel{+}{\mathrm{N}} \mathrm{O}_{2}$

Identify electrophilic centre in the following: $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{O}, \mathrm{CH}_{3} \mathrm{CN}, \mathrm{CH}_{3} \mathrm{I}$.

In which C-C bond of $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}$, the inductive effect is expected to be the least?

Write resonance structures of $\mathrm{CH}_{3} \mathrm{COO}^{-}$ and show the movement of electrons by curved arrows.

Write resonance structures of $\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CHO}$. Indicate relative stability of the contributing structures.

Explain why the following two structures, I and II cannot be the major contributors to the real structure of $\mathrm{CH}_{3} \mathrm{COOCH}_{3}$.

H₃C - C⁺ = O⁻         H₃C - C⁻ - O⁺
      |                  ||
     :O-CH₃              O-CH₃
      (I)                (II)

Explain why $\left(\mathrm{CH}_{3}\right)_{3} \stackrel{+}{\mathrm{C}}$ is more stable than $\mathrm{CH}_{3} \stackrel{+}{\mathrm{C}} \mathrm{H}_{2}$ and $\stackrel{+}{\mathrm{C}} \mathrm{H}_{3}$ is the least stable cation.

On complete combustion, 0.246 g of an organic compound gave 0.198 g of carbon dioxide and 0.1014 g of water. Determine the percentage composition of carbon and hydrogen in the compound.

In Dumas' method for estimation of nitrogen, 0.3 g of an organic compound gave 50 mL of nitrogen collected at 300 K temperature and 715 mm pressure. Calculate the percentage composition of nitrogen in the compound. (Aqueous tension at 300 K = 15 mm)

During estimation of nitrogen present in an organic compound by Kjeldahl's method, the ammonia evolved from 0.5 g of the compound in Kjeldahl's estimation of nitrogen, neutralized 10 mL of 1 M H₂SO₄. Find out the percentage of nitrogen in the compound.

In Carius method of estimation of halogen, 0.15 g of an organic compound gave 0.12 g of AgBr. Find out the percentage of bromine in the compound.

In sulphur estimation, 0.157 g of an organic compound gave 0.4813 g of barium sulphate. What is the percentage of sulphur in the compound?

What are hybridisation states of each carbon atom in the following compounds ? $\mathrm{CH}_{2}=\mathrm{C}=\mathrm{O}, \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2},\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}, \mathrm{CH}_{2}=\mathrm{CHCN}, \mathrm{C}_{6} \mathrm{H}_{6}$

Indicate the $\sigma$ and $\pi$ bonds in the following molecules : $\mathrm{C}_{6} \mathrm{H}_{6}, \mathrm{C}_{6} \mathrm{H}_{12}, \mathrm{CH}_{2} \mathrm{Cl}_{2}, \mathrm{CH}_{2}=\mathrm{C}=\mathrm{CH}_{2}, \mathrm{CH}_{3} \mathrm{NO}_{2}, \mathrm{HCONHCH}_{3}$

Write bond line formulas for : Isopropyl alcohol, 2,3-Dimethylbutanal, Heptan-4-one.

Which of the two: $\mathrm{O}_{2} \mathrm{NCH}_{2} \mathrm{CH}_{2} \mathrm{O}^{-}$ or $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{O}^{-}$ is expected to be more stable and why?

Explain why alkyl groups act as electron donors when attached to a $\pi$ system.

What are electrophiles and nucleophiles ? Explain with examples.

Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.

What is the difference between distillation, distillation under reduced pressure and steam distillation?

Discuss the chemistry of Lassaigne's test.

Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method and (ii) Kjeldahl's method.

Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.

Explain the principle of paper chromatography.

Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.

Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.

Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?

Will $\mathrm{CCl}_{4}$ give white precipitate of AgCl on heating it with silver nitrate? Give reason for your answer.

Why is a solution of potassium hydroxide used to absorb carbon dioxide evolved during the estimation of carbon present in an organic compound?

Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?

An organic compound contains 69% carbon and 4.8% hydrogen, the remainder being oxygen. Calculate the masses of carbon dioxide and water produced when 0.20 g of this substance is subjected to complete combustion.

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 H₂SO₄. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

0.3780 g of an organic chloro compound gave 0.5740 g of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound.

In the estimation of sulphur by Carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of barium sulphate. Find out the percentage of sulphur in the given compound.