Carbon & Its Compounds

Explanation: Ethane has 2 carbon atoms bonded to each other (1 C-C bond) and 6 hydrogen atoms bonded to carbons (6 C-H bonds).

Total = 1 + 6 = 7 Covalent bonds.

Explanation: The suffix ‘-one‘ indicates a Ketone group ($>C=O$).
-oic acid = Carboxylic acid
-al = Aldehyde
-ol = Alcohol

Explanation: Blackening is caused by soot (unburnt carbon particles). This happens during incomplete combustion when the air holes of the burner are blocked and the oxygen supply is insufficient.

Explanation: Carbon has 4 valence electrons and needs 4 more to complete its octet. Hydrogen has 1 and Chlorine has 7 valence electrons.

Carbon shares 3 electrons with 3 Hydrogen atoms and 1 electron with 1 Chlorine atom. This mutual sharing of electrons forms Covalent bonds.

(b) Hydrogen Sulphide ($H_2S$): S shares 1 electron with each H.

(c) Propanone ($CH_3COCH_3$): A ketone with 3 Carbons.

(d) Fluorine ($F_2$): Two F atoms share 1 electron pair.

Definition: A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.

Characteristics:
1. They differ by a $-CH_2-$ unit.
2. They differ by 14 u in molecular mass.
3. They have similar chemical properties.

1. Physical Properties:
– Smell: Ethanol has a sweet/pleasant smell. Ethanoic acid has a pungent smell (like vinegar).
– Melting Point: Ethanoic acid freezes in winter (Glacial acetic acid), Ethanol does not.

2. Chemical Properties (Carbonate Test):
– Ethanoic acid: Reacts with Sodium Carbonate to give brisk effervescence ($\text{CO}_2$ gas).
– Ethanol: No reaction with carbonates.

Explanation: Soap molecules have two ends:
1. Hydrophilic Head: Water-loving (Ionic end).
2. Hydrophobic Tail: Water-fearing (Carbon chain).

In water, the tails arrange themselves towards the oily dirt (away from water) and heads face outwards, forming a cluster called a Micelle.

In Ethanol: No micelle is formed because soap is fully soluble in ethanol, so the hydrophobic tails do not need to cluster away from the solvent.

1. High Calorific Value: They release a huge amount of heat energy upon burning.
2. Clean Burning: Saturated hydrocarbons burn with a clean blue flame without smoke.
3. Ignition: They have moderate ignition temperatures.

Hard water contains Calcium ($Ca^{2+}$) and Magnesium ($Mg^{2+}$) salts.

When soap reacts with these salts, it forms insoluble precipitates called Scum (Calcium or Magnesium Stearate). This scum makes cleaning difficult as it sticks to clothes.

Soap is a salt of a strong base (NaOH) and a weak acid (Fatty acid). Therefore, soap solution is Alkaline (Basic).

Observation:
– Red Litmus: Turns Blue.
– Blue Litmus: Remains Blue (No change).

Definition: The addition of Hydrogen to unsaturated hydrocarbons (alkenes) in the presence of a catalyst (Nickel/Palladium) to form saturated hydrocarbons is called hydrogenation.

Application: It is used in the industry to convert liquid vegetable oils (unsaturated) into solid vegetable ghee/vanaspati (saturated).

Addition reactions occur only in Unsaturated Hydrocarbons (compounds with Double or Triple bonds).

Saturated (Alkanes – $C_nH_{2n+2}$): $C_2H_6, C_3H_8, CH_4$. (No reaction).

Unsaturated (Alkenes/Alkynes):
1. $C_3H_6$ (Propene)
2. $C_2H_2$ (Ethyne)

Answer: $C_3H_6$ and $C_2H_2$.

– Cooking Oil (Unsaturated): It decolorizes the brownish color of Bromine water because it undergoes an addition reaction.

– Butter (Saturated): It does not decolorize Bromine water.

1. Soap molecules form Micelles in water.

2. The hydrophobic tail dissolves in the oil/dirt, while the hydrophilic head interacts with water.

3. When the water is agitated (rubbed/scrubbed), the micelles pull the oily dirt out of the fabric surface and trap it in the center of the micelle.

4. The dirt is then washed away with water as an emulsion, leaving the cloth clean.