Organic Chemistry: Some Basic Principles and Techniques quiz

The hybridisation of carbon in ethyne is:

The most stable carbocation is:

Which of these is a nucleophile?

The Prussian blue colour in Lassaigne's test indicates:

Steam distillation is used to purify:

Isomers with the same molecular formula but different functional groups show:

The IUPAC name of CH3CH2CHO is:

The Carius method is used to estimate:

Which effect is a temporary effect seen only in the presence of a reagent?

Glycerol is purified by:

Why is carbon able to form a large number of compounds? (2 marks)

What is metamerism? Give an example. (2 marks)

Why are free radicals highly reactive? (2 marks)

Distinguish between +R and -R effects. (2 marks)

Why is the carboxylate ion stabilised by resonance while the alkoxide ion is not? (2 marks)

Explain why Kjeldahl's method cannot be used for nitro compounds. (2 marks)

What is the principle of crystallisation? (2 marks)

How is sulphur detected in Lassaigne's extract? (2 marks)

What is column chromatography? (2 marks)

Why is oxygen estimated by difference? (2 marks)

0.2 g of an organic compound on complete combustion gave 0.44 g of CO2 and 0.18 g of water. Calculate the percentage of carbon, hydrogen and oxygen. (3 marks)

0.468 g of an organic compound gave 0.668 g of barium sulphate in the sulphur estimation. Calculate the percentage of sulphur (Ba = 137, S = 32, O = 16). (3 marks)

The ammonia from 0.75 g of a compound neutralised 15 mL of 0.5 M H2SO4. Calculate the percentage of nitrogen. (3 marks)

A compound contains 40% C, 6.67% H and the rest O. Calculate its empirical formula. (3 marks)

In TLC, a substance moves 2.4 cm and the solvent 6.0 cm. Calculate its Rf value. (3 marks)

Read the passage and answer the questions. A student was given an organic compound and asked to test for nitrogen. She fused it with sodium metal, extracted the fused mass with water and boiled the extract with iron(II) sulphate. On acidifying with sulphuric acid, a Prussian blue colour appeared. (i) What is the extract called? (ii) Which compound gives the Prussian blue colour? (iii) Why must the compound be fused with sodium? (5 marks)

Read the passage and answer the questions. Carbocations are classified as primary, secondary or tertiary depending on the number of carbon atoms attached to the positively charged carbon. The stability follows the order tertiary > secondary > primary > methyl. This order can be explained by the inductive effect and hyperconjugation. (i) What is the hybridisation of the carbon in a carbocation? (ii) How do alkyl groups stabilise a carbocation? (iii) What is the shape of a carbocation? (5 marks)

Read the passage and answer the questions. Chromatography is used to separate mixtures, purify compounds and test purity. It is based on the different rates at which components of a mixture are adsorbed on a stationary phase as a mobile phase moves over it. In thin layer chromatography, a thin layer of silica gel is spread on a glass plate. (i) What are the stationary and mobile phases in TLC? (ii) How are colourless spots detected? (iii) What does a higher Rf value indicate? (5 marks)

Read the passage and answer the questions. Organic compounds can be named using common names or IUPAC names. The IUPAC system uses a word root for the number of carbon atoms in the longest chain, a primary suffix for saturation, and a secondary suffix for the functional group. Prefixes are used for substituents. (i) Write the IUPAC name of CH3CH(OH)CH3. (ii) Write the IUPAC name of CH3COCH2CH3. (iii) Write the structural formula of 2-methylpropane. (5 marks)

Read the passage and answer the questions. Aniline is a liquid that decomposes at its boiling point. It is volatile in steam and immiscible with water. Glycerol also decomposes at its boiling point but is not steam-volatile. (i) Which method is used to purify aniline? (ii) Which method is used for glycerol? (iii) Explain the principle of steam distillation. (5 marks)

Explain the representation of organic compounds by different structural formulae with examples. Explain the classification and IUPAC nomenclature of organic compounds. (6 marks)

Explain structural isomerism and its types with examples. (6 marks)

Explain the electronic displacements in covalent bonds: inductive, resonance, electromeric effects and hyperconjugation. (6 marks)

Describe the methods of purification of organic compounds, including distillation and chromatography. (6 marks)

Explain the qualitative and quantitative analysis of organic compounds, including Lassaigne's test and the estimation of carbon, hydrogen, nitrogen and halogens. (6 marks)