(i)

(ii) 

(a) (i)

functional group is aldehyde. - CHO.
(ii)
 
functional group is aldehyde. - CHO.
(b) General formula is C_nH_2nO.
(c) Both (i) and (ii) are forming a homologous series of compounds containing aldehyde functional group. Structure of fourth member of this homologous series is

(i) The elements P and R will form covalent bond with carbon because both the elements accept electrons to form ionic as well as covalent bonds.
While element Q (2, 8, 1) donates one electron to form ionic compounds and element 'S' (2, 8, 8) is stable due to complete octet in valence shell. Hence, they do not form covalent bond with carbon.
(ii) Carbon reacts with an element in table to form several compounds because of
(a) Tetravalency of carbon Carbon has electronic structure of (2, 4). Thus, it has four electrons in outermost shell. It is capable of bond formation with four other elements.
(b) Catenation Due to small size, C-C bond is strong. This allow carbon to form long chain compound of different size.

(i) Distinction based on physical properties:
(a) Smell Ethanoic acid has a pungent smell.
Ethanol has a pleasant smell.
(b) Melting point Ethanol has lower melting point (156 K) than ethanoic acid (290 K).
(c) Physical state Ethanoic acid is solid (glacial acetic acid) in winters but ethanol is always a liquid.
(ii) Distinctions based on chemical properties:
(a) Reaction with sodium hydrogen carbonate On adding a small amount of sodium hydrogen carbonate to ethanoic acid, carbon dioxide gas is evolved with brisk effervescence. However, no such reaction noticed in case of ethanol.
CH₃COOH + NaHCO₃ \(\rightarrow\) CH₃CO\(\bar{O}\)\(\overset{+}{N}\)a + CO₂\(\uparrow\) H₂O
Ethanoic acid
C₂H₅OH + NaHCO₃ \(\rightarrow\) No reaction
Ethanol
(b) Reaction with caustic alkalies Ethanoic acid reacts with both sodium hydroxide (NaOH) and potassium hydroxide (KOH) to form corresponding salt and water. Ethanol fails to react with either of these.
CH₃COOH + NaOH \(\rightarrow\) CH₃CO\(\bar{O}\)\(\overset{+}{N}\)a + H₂O
CH₃COOH + KOH \(\rightarrow\) CH₃CO\(\bar{O}\)\(\overset{+}{K}\) + H₂O

Substances that are capable of providing oxygen to other substances are called oxidising agents. Alkaline potassium permanganate (KMnO₄) or acidified potassium dichromate (K₂Cr₂O₇) act as an oxidising agent in oxidising alcohols into acids.

(i) Hydrogenation reaction The addition of hydrogen to an unsaturated compound to make it saturated is known as hydrogenation.
e.g. \(\underset{\text { Ethene }}{\mathrm{CH}_2}=\mathrm{CH}_2+\mathrm{H}_2 \xrightarrow[\mathrm{Ni}]{200^{\circ} \mathrm{C}} \underset{\text { Ethane }}{\mathrm{CH}_3-\mathrm{CH}_3}\)
(ii) Oxidation reaction The reaction in which an oxygen is added to the substance or removal of hydrogen is called oxidation reactions.
e.g. \(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH} \xrightarrow[\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7]{[\mathrm{O]}} \mathrm{CH}_3 \mathrm{COOH}\)
In the above reaction oxygen is added to ethanol, CH₃CH₂OH therefore it is an oxidation reaction.
(iii) Substitution reaction The reaction in which a reagent substitutes (or replaces) an atom or a group of atoms from the reactant (substrate) are called substitution reactions.
e.g. \(\mathrm{CH}_4+\mathrm{Cl}_2 \xrightarrow{\text { Sunlight }} \mathrm{CH}_3 \mathrm{Cl}+\mathrm{HCl}\)
(iv) Saponification reaction When esters are hydrolysed in the presence of a base (NaOH) to get back an alcohol and sodium salt of an acid then reaction is called saponification reaction. It is used in the preparation of soaps.
e.g. \(\mathrm{CH}_3 \mathrm{COOCH}_3+\mathrm{NaOH} \longrightarrow\) \(\mathrm{CH}_3 \mathrm{CO\overline{\mathrm{O}}} \stackrel{+}{\mathrm{Na}}+\mathrm{CH}_3 \mathrm{OH}\)
(v) Combustion reaction Organic compounds burn in oxygen and yield majorly CO₂, heat and light. This reaction is known as combustion reaction.
e.g. \(\mathrm{CH}_4+2 \mathrm{O}_2 \longrightarrow \mathrm{CO}_2+2 \mathrm{H}_2 \mathrm{O}+\text { Energy }\)

Soaps are sodium salts of fatty acids. It is biodegradable and shows cleansing action by removing dirt.
Mechanism of cleansing action:
Soap molecule has two ends, the charged end that gets attracted towards water is called hydrophilic and the long carbon chain that repels water is called hydrophobic tail. When soap is dissolved in water, the carbon chain i.e., hydrophobic end gets attracted towards the oil, dirt and grease. The hydrophilic end stays away from this. ' The micelle formation takes place. The tail entangles dirt, oil or grease, if required, the agitation is done. Lot of rinsing is done with water so that water molecules attract charged (Na+) end and carries the soap molecules with dirt attached to it and clean the clothes, utensils, etc:

Scum formation: Hard water often contains salts of calcium and magnesium. Soap molecules react with the salts of calcium and magnesium and form a precipitate. This precipitate begins floating as an off-white layer over water. This layer is called scum. soaps lose their cleansing property in hard water because of formation of scum.
In case of detergents, the salts present in hard water does not react with the molecules of detergent to form insoluble scum, but the molecules of detergent remain as it is and helps in the cleansing action.

Carbon has 4 electrons in its valence shell. To complete its octet, it either needs to gain 4 electrons or lose 4 electrons to the other atom. Both these processes are impossible. Therefore, carbon atom achieve noble gas configuration by sharing 4 electrons with other atoms of itself or atoms of other elements. The bonds that are formed by sharing electrons are known as covalent bond. In covalent bonding, both atoms share the valence electrons, i.e. the shared electrons belong to the valence shells of both the atoms. CH₃CI is called chloromethane, which contains 1  carbon atom, 3 hydrogen atoms and 1 chlorine atom.
Electronic configuration of carbon,6 = \(\overset{K}{2}\), \(\overset{L}{4}\)
Electronic configuration of hydrogen, 1 = \(\overset{K}{1}\)
Electronic configuration of chlorine, 17= \(\overset{K}{2}, \overset{L}{8}, \overset{M}{7}\)
Carbon atom has four outermost electrons, each hydrogen atom has one electron and chlorine has seven outermost electrons. Carbon shares its four outermost electrons with 3 hydrogen atoms and 1 chlorine atom to form CH₃Cl as follows:
 

Butanal

'A' belongs to alkyne as general formula of alkyne is C₂H_2n−2
'B' belongs to alkene as general formula of alkene is C₂H_2n

Both carbon and silicon have  similar valence shell electronic configuration that is each has four electrons in the valence shell and hence show the phenomenon of catenation. But carbon being smaller than silicon forms stronger c-C than Si-Si bonds. Thus due to greater strength of C-C over Si-Si bonds, carbon shows catenation to a greater extent than silicon.

Hard water contains calcium and magnesium ions. Soap is basically sodium or potassium salt of higher fatty acids. When soap is added to hard water, corresponding calcium and magnesium salts are formed, which being insoluble gets precipitated. These precipitates are called scum. Reactions taking place are shown as:
Ca²⁺          + 2RCOONa \(\rightarrow\) (RCOO)₂ Ca\(\downarrow\) + 2Na⁺
Hard water      Soap               Calcium salt precipitate
Mg²⁺ + 2R COONa \(\rightarrow\) (RCOO)₂Mg \(\downarrow\) + 2Na⁺
Hard water  Soap           Magnesium salt precipitate 

Take 1 mL ethanol and 1 mL glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube. Warm in a water-bath for at least five minutes. Pour into a beaker containing 20-50 mL of water.
1.Pleasant fruity smelling compound is obtained called ester. Such a chemical reaction is called esterification .
\(\underset{Ethanoic\ acid}{C{H}_{3}}-COOH+\underset{\ Ethanol}{C{H}_{3}-C{H}_{2}-C{H}_{2}OH}\underset{dehydrating\ agent}{\overset{Conc.{H}_{2}S{O}_{4}}{\leftrightharpoons }}\underset{Ester}{C{H}_{3}COO{C}_{2}{H}_{5}}+\underset{Water}{{H}_{2}O}\) 

Heating of different carbon compounds, observing the flame and smoke

Alcohol and acetone bums with non-sooty flame-complete combustion takes place.
Camphor, naphthalene burns with sooty flame-(unsaturated hydrocarbons) incomplete combustion takes place.

(i) (d): A and F are alkanes; Band E are alkenes; C and D are alkynes.
(ii) (d): B is an alkene having general formula C_nH_2n, the homologous series to which E belongs.
(iii) (a) : C and D belong to a homologous series having general formula C_nH_2n-2 .Band E are alkenes. All the compounds have different physical and chemical properties.
(iv) (b): (B) is alkene.
(v) (d): (F) is an alkane.

(c): In alcohols -OH group is attached to an alkyl group hence water and alcohol have different properties.

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