(a) A saturated organic compound 'A' belongs to the homologous series of alcohols. On heating 'A' with concentrated sulphuric acid at 443 K, it forms an unsaturated compound 'B' with molecular mass 28 u. The compound 'B' on addition of one mole of hydrogen in the presence of Nickel, changes to a saturated hydrocarbon 'C'. (i) Identify A, B and C. (ii) Write the chemical equations showing the conversion of A into B. (iii) What happens when compound C undergoes combustion? (iv) State one industrial application of hydrogenation reaction. (v) Name the products formed when compound A reacts with sodium. OR (b) (i) With the help of diagram, show the formation of micelles, when soap is applied on oily dirt. (ii) Take two test tubes X and Y with $10\mathrm{mL}$ of hard water in each. In test tube 'X', add few drops of soap solution and in test tube 'Y' add a few drops of detergent solution. Shake both the test tubes for the same period. (1) In which test tube the formation of foam will be more? Why? (2) In which test tube is a curdy solid formed? Why?

PART (a)

(i) Identification of A, B, and C:

• Compound A is Ethanol ($CH_3CH_2OH$ or $C_2H_5OH$).
• Compound B is Ethene ($CH_2=CH_2$ or $C_2H_4$). Its molecular mass is calculated as:

$$(2 \times 12) + (4 \times 1) = 24 + 4 = 28\text{ u}$$

• Compound C is Ethane ($CH_3CH_3$ or $C_2H_6$).

(ii) Chemical Equation for the conversion of A into B (Dehydration):

$$CH_3CH_2OH \xrightarrow{\text{Hot conc. } H_2SO_4, 443\text{ K}} CH_2=CH_2 + H_2O$$

(Here, concentrated sulphuric acid acts as a dehydrating agent.)

(iii) Combustion of Compound C (Ethane):

When ethane undergoes complete combustion in the presence of oxygen, it burns with a clean blue flame to produce carbon dioxide gas, water vapor, heat, and light.

$$2C_2H_6 + 7O_2 \rightarrow 4CO_2 + 6H_2O + \text{Heat} + \text{Light}$$

(iv) Industrial Application of Hydrogenation:

Hydrogenation is used industrially to convert liquid vegetable oils (unsaturated fats) into solid vanaspati ghee (saturated fats) using a nickel ($Ni$) catalyst.

(v) Reaction of Compound A (Ethanol) with Sodium:

When ethanol reacts with sodium metal, it forms sodium ethoxide and releases hydrogen gas.

$$2CH_3CH_2OH + 2Na \rightarrow 2CH_3CH_2ONa + H_2\uparrow$$

PART (b)

(i) Micelle Formation:

Soap molecules consist of two parts:

1. A hydrophilic (water-loving) ionic head (e.g., $-COO^-Na^+$) which points outwards towards water.
2. A hydrophobic (water-fearing) hydrocarbon tail which points inwards, away from water, attaching itself to the oily dirt.

When soap is applied to oily dirt, the hydrophobic tails align towards the center to dissolve in the oil droplet, while the ionic heads face outwards into the aqueous medium. This unique spherical cluster of soap molecules trapping the dirt at the center is called a micelle.

(ii) Test Tube X (Soap + Hard Water) vs Test Tube Y (Detergent + Hard Water):

1. More Foam Formation: Test tube Y will show more foam formation. Detergents are sodium salts of sulfonic acids or ammonium salts with chlorides or bromides. Their charged ends do not form insoluble precipitates with the calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$) ions present in hard water. Thus, they remain effective and lather easily.
2. Curdy Solid Formation: Test tube X will show the formation of a curdy solid (scum). Soap reacts with the calcium and magnesium salts present in hard water to form insoluble calcium and magnesium salts of fatty acids, which precipitate out as a sticky, curdy white solid.