Answer the questions.[Che-2M]

Question 12 Marks

What is saponification? Write the reaction involved in this process.

Answer

When ester treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. This can be given by following equation.
CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

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Question 22 Marks

Explain the given reaction with the example:

Substitution reaction.

Answer

Saturated hydrocarbons are fairly unreactive. But in the presence of sunlight, chlorine substitutes hydrogen one by one.

CH₄ + Cl₂ → CH₃Cl + HCl (in the presence of sunlight)

This substitution can go on till, carbon tetrachloride is obtained.

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Question 32 Marks

Explain the given reaction with the example:

Saponification reaction.

Answer

When ester is treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. This can be given by following equation.
CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

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Question 42 Marks

Explain the given reaction with the example:

Oxidation reaction.

Answer

When oxygen is added to alcohol to make carboxylic acid, this is called oxidation reaction. Following is an example of oxidation of alcohol.

$\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\xrightarrow{\ \ \text{alk KMnO}_4/\alpha\ \text{idified K}_2\text{Cr}_2\text{O}_7}\text{CH}_3\text{CH}_2\text{COOH}$

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Question 52 Marks

Explain the given reaction with the example:

Hydrogenation reaction.

Answer

Addition of hydrogen to unsaturated hydrocarbon to obtain a saturated hydrocarbon is called hydrogenation reaction. Hydrogenation is used for converting unsaturated vegetable oil into fat. This can be shown by following equation:

$\text{R}_2\text{C}=\text{CR}_2+\text{H}_2\xrightarrow{\ \ \ \text{Ni}\ \ \ }\text{R}_2\text{C}-\text{CR}_2\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ |\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{H}\ \ \ \ \ \text{H}$

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Question 62 Marks

Explain the given reaction with the example:

Combustion reaction.

Answer

When a substance burns in the presence of oxygen, the reaction is called combustion. Following is an example of combustion reaction.

CH₄ + O₂ → CO₂ + H₂O + heat and light

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Question 72 Marks

Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Compare the ability of catenation of the two elements. Give reasons.

Answer

Both carbon and silicon show the ability of catenation. But compounds made by silicon are reactive and less stable. On the other hand, bonds formed by carbon are very strong and hence organic compounds are more stable than silicon compounds. It can be said that carbon shows better catenation ability than silicon.

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Question 82 Marks

Carbon, Group (14) element in the Periodic Table, is known to form compounds with many elements.
Write an example of a compound formed with,

Chlorine (Group 17 of Periodic Table)
Oxgygen (Group 16 of Periodic Table)

Answer

The compound is carbon tetrachloride (CCl₄)
The compound is carbon dioxide (CO₂)

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Question 92 Marks

A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.

Answer

When ethanol reacts with sodium, then hydrogen gas is evolved. This reaction can be given by following equation:

2Na + 2CH₃CH₂OH → 2CH₃CH₂ONa + H₂

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