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In the question two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct
answer to these questions from the codes (i), (ii), (iii) and (iv) as given below. Assertion (A) : Carbon has a strong tendency to either lose or gain electrons to attain noble gas configuration. Reason (R) : Carbon has four electrons in its outermost shell and has the tendency to share electrons with carbon or other                       elements.
Option: 1 Both (A) and (R) are true and (R) is correct explanation of the assertion (A).
Option: 2 Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
Option: 3 (A) is true, but (R) is false.
Option: 4 (A) is false, but (R) is true.

(A) is false, but (R) is true.

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In the following question, two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select
the correct answer to these question from the codes (a), (b), (c) and (d) as given below : Assertion (A) : Following are the members of a homologous series :
CH_{3}OH, CH_{3}CH_{2}OH, CH_{3}CH_{2}CH_{2}OH
Reason (R) : A series of compounds with same functional group but differing by – CH_{2} – unit is called a homologous series.
Option: 1 Both (A) and (R) are true and (R) is correct explanation of the assertion.
 
Option: 2 Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
 
Option: 3 (A) is true but (R) is false.
 
Option: 4 (A) is false but (R) is true.

1.CH_{3}OH, CH_{3}CH_{2}OH, CH_{3}CH_{2}CH_{2}OH  are the members of a homologous series.
2. A series of compounds with the same functional group but differing by – CH_{2} – unit is called a homologous series.

Both (A) and (R) are true and (R) is the correct explanation of the assertion

Hence Option A is correct. 

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In the Question two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct
answer to these questions from the codes (a), (b), (c) and (d) as given below : Assertion (A) : Ethanoic acid is also known as glacial acetic acid. Reason (R) : The melting point of pure ethanoic acid is 290\; Kand hence it often freezes during winters in cold climates.
Option: 1 Both (A) and (R) are true and (R) is correct explanation of the assertion.
Option: 2 Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
Option: 3 (A) is true but (R) is false.
Option: 4 (A) is false but (R) is true.

Both (A) and (R) are true and (R) is correct explanation of the assertion.

Hence option A is correct 

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Covalent compounds have low melting and boiling point. Why ?
 

Covalent compounds have low melting and boiling point because of weak intermolecular forces.

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In the question, two statements are given - one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these question from the codes (a),(b),(c) and (d) as given below : Assertion (A) : Esterification is a process in which a sweet smelling substance is produced. Reason (R) :  When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.
Option: 1 Both A and R are true and R is correct explanation of the Assertion.
Option: 2 Both A and R are true but R is not the correct explanation of the Assertion.
Option: 3 A is true but R is false.
Option: 4 A is false but R is true.

  •  Esterification is a process in which a sweet smelling substance is produced.
  • When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.

Both A and R are true but R is not the correct explanation of the Assertion.

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An organic compound A on heating with concentrated H_2SO_4  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 CO_2  and 3 moles of H_2O. Identify the compounds A, B and C and write the chemical equations of the reactions involved.

As the compound on combustion forms two moles of carbon dioxide and 3 moles of water, it means that 2 carbon atoms and 6 hydrogen atoms are present. So molecular formula is C2H6 (ethane).

C_2H_6 + 3.5 O_2 \rightarrow 2CO_2 + 3H_2O

Compound A is ethanol (CH3CH2OH). On dehydrogenation, it gives ethene.

C_2H_5OH \overset{Hot conc. H_{2}SO_{4}}{\rightarrow}C_{2}H_{4}+H_{2}O

Compound B is ethene (CH_2=CH_2)

Compound is C is obtained by addition of 1 mole hydrogen in presence of nickel to B which means C is ethane

C_{2}H_{4}+H_{2}\overset{Ni}{\rightarrow}C_{2}H_{6}

Compound C is CH_3-CH_3

C_{2}H_{6}+7O_{2}\rightarrow4CO_{2}+6H_{2}O+Heat+Light

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Explain the given reactions with the examples 

(a) Hydrogenation reaction 

(b) Oxidation reaction 

(c) Substitution reaction 

(d) Saponification reaction 

(e) Combustion reaction

(a) Hydrogenation reaction is addition of hydrogen to unsaturated molecule of a hydrocarbon.

Oils are unsaturated compounds containing double bonds. Unsaturated compounds are the only one which can undergo addition reaction.

The reaction is known as hydrogenation reaction. For example:

Hydrogenation reactions are addition reactions

 

(b) Oxidation reaction: A reaction in which an organic compound is reacted with an oxidizing agent where hydrogen is removed or oxygen is added to the compound.

For example:

Alcohol \rightarrow Aldehyde/Ketone \rightarrow Carboxylic acid

CH_{3}CH_{2}OH \overset{Alk. KMnO_{4}}{\rightarrow}CH_{3}COOH

 

(c) Substitution reaction is when atom or group of atoms are replaced with other atom or group of atoms.

CH_4 + Cl_2 \overset{hv}{\rightarrow} CH_3Cl + HCl

(d) When an ester is heated with sodium hydroxide solution, ester gets hydrolyzed (breaks down) to form the parent alcohol and sodium salt of carboxylic acid.

Example:

CH_3COOCH_3 + NaOH \overset{Alk. KMnO_{4}}{\rightarrow} CH_3COONa + CH_3OH

(e) Combustion Reaction is where an organic compound reacts with oxygen to form carbon dioxide and water vapor.

CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + Heat + Light

 

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Draw the possible isomers of the compound with molecular formula C_3H_6O and also give their electron dot structures. 

For C_3H_6O

1) Propanal

2) Acetone

3) Methoxyethane

H_{2}C=CH-O-CH_{3}

4) trans-1-propenol

5) cis-1-propenol

6) 2-propen-2-ol

7) 2-propen-1-ol

8) oxacyclobutane

      

9) cyclopropanol

10 and 11) Enantiomers of methyl oxirane:

(S)-Methyloxirane                                    (R)-Methyloxirane

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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. 

(a) When Ethanol is reacted with concentrated Sulphuric acid in the presence of heat it will lead to removal of water molecule and forms ethene. This type of reaction is called dehydrogenation reaction.

CH_3CH_2OH \overset{conc. H_{2}SO_{4}}{\rightarrow} CH_2=CH_2 + H_2O

(b)  When propanol is heated in the presence of potassium permanganate, it will convert to propanoic acid. This type of reaction is called oxidation reaction.

                      CH_3CH_2CH_2OH \overset{Alk. KMnO_{4}}{\rightarrow} CH_3CH_2COOH

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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?

 

(a) Calcium hydroxide or Limewater (Ca(OH)_2) taken in tube B turns milky when carbon dioxide passes through it as it forms Calcium carbonate (CaCO_3)

Ca(OH)_2 (aq) + CO_2 (g) \rightarrow CaCO_3 (s) + H_2O (l)

(b) Test Tube A

Sodium Carbonate reacts with ethanoic acid to form sodium ethanoate, carbon dioxide and water

Na_2CO_3 + CH_3COOH \rightarrow CH_3COONa + CO_2 + H_2O

 Test Tube B

Calcium hydroxide turns milky white due to formation of Calcium carbonate (CaCO3) when Carbon dioxide is passed through it.

Ca(OH)_2 (aq) + CO_2 (g) \rightarrow CaCO_3 (s) + H_2O (l)

(c) No change will take place when we take ethanol instead of ethanoic acid.

CH_3CH_2OH + Na_2CO_3 \rightarrow \text{ NO REACTION}

(d) Take a small piece of Calcium oxide in a test tube. Add water to it, part of it gets dissolved but majority of it gets suspended. So pass the complete solution into a filter paper and collect it in a test tube and this solution is lime water.

CaO + H_2O \rightarrow Ca(OH)_2

 

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