Chapter 4: Carbon and Its Compounds

Q53Written answer

Look at Figure 4.1 and answer the following questions

(a) What change would you observe in the calcium hydroxide solution taken in tube B?

(b) Write the reaction involved in test tubes A and B respectively.

(c) If ethanol is given instead of ethanoic acid, would you expect the same change?

(d) How can a solution of lime water be prepared in the laboratory?

chemical reaction

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Calcium Hydroxide solution would become milky
Reaction in Tube A

CH₃COOH+NAHCO₃ →CH₃COONA+CO₂+ H₂O

Reaction in tube B

Ca(OH)₂+CO₂ CaCO₃+H₂O

Ethanol will not react with Sodium Hydrogen carbonate. Hence same change will not be observed.
In a beaker take distilled water and mix Calcium carbonate powder and mix thoroughly. Allow the solution to settle and decant the clear solution to obtain the lime water.

Q54Written answer

How would you bring about the following conversions? Name the process and write the reaction involved.

(a) ethanol to ethene.

b) propanol to propanoic acid. Write the reactions.

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Worked solution

Ethene is formed when ethanol is heated at 443 K with an excess of concentrated sulphuric acid.

CH₃CH₂OH Con H₂SO₄ CH₂=CH+H₂O

Propanol is treated with alkaline Potassium permanganate or acidified Potassium-di-chromate to obtain propanoic acid.

CH₃CH₂CH₂OH Alk KMnO₄/ acidified K₂Cr₂O₇ CH₃CH₂COOH

Q55Written answer

Draw the possible isomers of the compound with molecular formula C3H6O and also give their electron dot structures.

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isomers of C3H6O

Q56Written answer

Explain the given reactions with the examples

(a) Hydrogenation reaction

(b) Oxidation reaction

(c) Substitution reaction

(d) Saponification reaction

(e) Combustion reaction

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(a) Hydrogenation reaction can be defined as an addition reaction between the hydrogen and other compounds in the presence of a catalyst.

CH₂ = CH₂ → CH₃CH₃

(b) An oxidation reaction is a reaction in which oxygen combines with an element or a compound. In other words, it can also be defined as a molecule loses its electrons.

2Mg + O₂→ 2MgO

(c) Substitution reaction can be defined as the reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.

Zn + CuSO4 → ZnSO4 + Cu

(d) Saponification reaction is the reaction in which the hydrolysis of an ester takes place with NaOH or KOH to give alcohol and sodium or potassium salt of the acid.

CH₃COOC₂H₅ + NaOH → C₂H₅OH + CH₃COONa

(e) Combustion reaction is the reaction in which oxygen combines with a compound to form carbon dioxide and water. These reactions are exothermic, meaning they give off heat.

CH₄ + 2O₂ → 2H₂O + CO₂

Q57Written answer

An organic compound A on heating with concentrated H2 SO4 forms a compound B which on addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of CO2 and 3 moles of H2O. Identify the compounds A, B and C and write the chemical equations of the reactions involved.

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Worked solution

Compound A is Ethanol

Compound A = CH₃CH₂OH

CH₃C_H2OH (in the presence of conc. H₂SO₄) → CH₂-CH₂+ H₂O

Compound B is Ethene

Compound B is CH₂= CH₂

CH₂=CH₂ (in the presence of Ni) →C₂H₆

Compound C = CH3 — CH3

2C₂H₆+7O₂ 4CO₂ +6H₂O

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so compound S is Ester or Ethyl ethanoate and compound A is Ethanol