(a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:

(i) Physical state

(ii) Taste

(iii) $\text{NaHCO}_3$ test

(iv) Ester test

(b) Write a chemical reaction to show the dehydration of ethanol.

OR

(a) What is a soap? Why are soaps not suitable for washing clothes when the water is hard?

(b) Explain the action of soap in removing an oily spot from a piece of cloth.

PART (a)

Table: Differentiation between Ethanol and Ethanoic Acid

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PART (b)

Dehydration of Ethanol:

Heating ethanol at $443\text{ K}$ with excess concentrated sulphuric acid ($\text{H}_2 ext{SO}_4$) results in its dehydration to yield ethene:

$$\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Hot conc. } \text{H}_2\text{SO}_4, 443\text{ K}} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O}$$

Here, concentrated sulphuric acid acts as a dehydrating agent as it removes water from ethanol.

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OR OPTION

(a) Soap and its behavior in Hard Water:

• Soap: Soaps are sodium or potassium salts of long-chain carboxylic acids (fatty acids).
• Why soaps are not suitable for hard water: Hard water contains calcium (${\text{Ca}}^{2+}$) and magnesium (${\text{Mg}}^{2+}$) ions. When soap is used with hard water, these divalent ions react with the soap molecules to form an insoluble, sticky precipitate called scum:

$$\text{Soap} + \text{Ca}^{2+}/\text{Mg}^{2+} \rightarrow \text{Insoluble Scum (Precipitate)}$$

This scum sticks to the clothes and prevents the soap from lathering easily, making the washing process highly inefficient and wasting a large amount of soap.

(b) Cleansing Action of Soap (Removal of an Oily Spot):

1. A soap molecule has two distinct parts:

• A hydrophilic head (ionic end, e.g., $-\text{COO}^-\text{Na}^+$) which is water-soluble.
• A hydrophobic tail (long hydrocarbon chain) which is oil-soluble (water-insoluble).

1. When soap is dissolved in water containing a dirty cloth with an oily spot, the hydrophobic tails align themselves towards the oil droplet, while the ionic hydrophilic heads face outwards towards the water.
2. This unique orientation forms a spherical cluster of molecules called a micelle.
3. The oily dirt is trapped securely at the center of the micelle.
4. Because the outer heads are negatively charged, the micelles repel each other and do not precipitate. When the water is agitated, these micelles containing the trapped grease are easily washed away, leaving the cloth clean.