1. (a) Basic magnesium
carbonate (Note: Often accepted as the layer formed due to moist air,
though pure oxide is also common context)
2. (d) Decomposition of calcium
carbonate to form quick lime and carbon dioxide
3. (a) Water < Acetic acid <
Hydrochloric acid
4. (a) Ductility
5. (c) Mercury
6. (d) -CHO
7. (b) Butanol
8. (c) Sour and change blue litmus
to red
9. (d) Potassium
10. (a) Metal oxides which react
with both acids and bases
11. (c) Galvanization
12. (c) Sodium ethoxide and
hydrogen
13. (b) Iron sulphate
14. (c)
CaSO4.1/2H2O
15. (a) Group 16, Period 3
16. (b) Neon
17. (c) Carbon dioxide
18. (c) Reduction
19. (c) CCl4
(Carbon tetrachloride is a covalent compound)
20. (c) 5% - 8% acetic acid in
water
21.
The blue colour of copper sulphate solution fades and turns light green due to the
formation of Iron (II) Sulphate. Iron is more reactive than copper and displaces
it.
Equation: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
22.
Role: HCl in the stomach kills bacteria entering with food and provides an acidic
medium for the enzyme Pepsin to act.
Excess: If produced in excess, it causes pain and irritation, leading to acidity or
ulcers.
23.
Ionic compounds are held together by strong electrostatic forces of attraction between
oppositely charged ions. A considerable amount of energy is required to break these strong inter-ionic
attractions, resulting in high melting points.
24.
(i) Methane (CH4): Carbon shares 4 electrons with 4 Hydrogen atoms.
(ii) CO2: Carbon shares 2 pairs of electrons with each Oxygen atom (Double
bonds).
25.
| Roasting |
Calcination |
| Heating ore in presence of excess air. |
Heating ore in absence/limited supply of air. |
| Used for Sulphide ores. |
Used for Carbonate ores. |
| Ex: 2ZnS + 3O2 → 2ZnO + 2SO2 |
Ex: ZnCO3 → ZnO + CO2 |
26.
Reason: To prevent oxidation (rancidity) of the fats/oils which
results in bad taste and smell. Nitrogen is an inert gas and prevents contact with oxygen.
Term: Rancidity.
27.
(a) Gas Y: Hydrogen (H2).
(b) Test: Bring a burning candle near the gas bubbles. The gas burns with a
characteristic pop sound.
(c) Equation: Zn(s) + H2SO4(aq) → ZnSO4(aq) +
H2(g)
28.
Homologous Series: A series of organic compounds having the same functional group and
similar chemical properties, in which successive members differ by a -CH2 group.
Characteristics:
1. Same general formula.
2. Gradation in physical properties (like boiling point) with increasing mass.
29.
Cleansing Action: Soap molecules have two ends: Hydrophilic (ionic) head and
Hydrophobic (carbon chain) tail. The hydrophobic tail attaches to dirt/oil (grease), while the
hydrophilic head points outwards to water. They form structures called micelles,
trapping the dirt in the center, which is washed away with water.
Hard Water: Calcium and Magnesium ions in hard water react with soap to form an
insoluble substance called Scum, reducing effectiveness.
30.
(i) CaCO3 + 2HCl → CaCl2 + H2O +
CO2
(ii) 3MnO2 + 4Al → 3Mn + 2Al2O3 + Heat
(iii) 3Fe + 4H2O(g) → Fe3O4 + 4H2
31.
Formation of MgCl2:
Mg (2,8,2) loses 2 electrons to form Mg2+.
Two Cl atoms (2,8,7) each gain 1 electron to form 2Cl-.
The electrostatic attraction between Mg2+ and 2Cl- forms MgCl2.
Nature of Bond: Ionic Bond (Electrovalent Bond).
32.
Exothermic: Respiration involves the breakdown of glucose with oxygen to release a
large amount of energy for life processes. Since energy is released, it is exothermic.
Equation: C6H12O6 + 6O2 →
6CO2 + 6H2O + Energy
33.
Structural Isomers: Compounds with same molecular formula but different structural
arrangement of atoms.
Butane (C4H10):
1. n-Butane (Straight chain)
2. Iso-butane (Branched chain / 2-methylpropane)
34.
(a) Water of Crystallization: The fixed number of water molecules chemically attached
to each formula unit of a salt.
Ex: Copper Sulphate (CuSO4.5H2O), Washing Soda
(Na2CO3.10H2O).
(b) Reaction: Plaster of Paris absorbs water to form a hard solid mass called
Gypsum.
CaSO4.1/2H2O + 1½H2O → CaSO4.2H2O
(Gypsum)
(c) Bleaching Powder: Prepared by action of chlorine gas on dry slaked lime.
Ca(OH)2 + Cl2 → CaOCl2 + H2O
Uses: 1. Bleaching cotton/linen/wood pulp. 2. Disinfecting drinking water.
35.
(a) Differences:
(i) State: Ethanol is liquid at room temp; Ethanoic acid freezes in cold (glacial).
(ii) Na2CO3: Ethanol has No reaction. Ethanoic
acid reacts to release CO2 gas (brisk effervescence).
(b) Esterification:
CH3COOH + C2H5OH → CH3COOC2H5
(Ethyl Ethanoate) + H2O
Product: Ester (Sweet smelling substance).
(c) Role of Conc. H2SO4: It acts as a dehydrating
agent (removes water).
36.
(a)
(i) Corrosion: The eating away of metals by action of air, moisture, or chemicals. Ex:
Rusting of Iron (Reddish brown coating).
(ii) Rancidity: Oxidation of fats/oils in food causing bad smell/taste. Ex: Chips
packet tasting bad after being open.
(b)
Iron filings added to:
- Al2(SO4)3: No reaction (Fe is less reactive than Al).
- CuSO4: Blue to Green (Fe displaces Cu). Reaction: Fe + CuSO4
→ FeSO4 + Cu.
- FeSO4: No reaction.
(c) Tin (Sn) is less reactive than Zinc. If Zinc were used, it might react with organic
acids in the food, which could be harmful. Tin is more stable.
37.
(i) Basic.
(ii) Antacids are mild bases (like Mg(OH)2) that neutralize excess acid in
the stomach.
(iii) The soil is Acidic. Quick lime (Calcium Oxide) is basic in
nature and is used to neutralize the acidity of the soil to make it suitable for crops.
38.
(i) Because the products formed are Chlorine (Chlor) and Sodium Hydroxide (Alkali).
(ii) Anode: Chlorine gas (Cl2). Cathode: Hydrogen gas (H2).
(iii) 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) +
H2(g).
Use of H2: Fuels, Margarine, Ammonia for fertilizers.
39.
(i) Potassium (K).
(ii) No. Copper is less reactive than Iron (below Iron in series), so
it cannot displace Iron.
(iii) Zinc is more reactive than Copper. The blue color of copper sulphate fades
(becomes colorless/ZnSO4) and reddish-brown copper metal is deposited.
Zn + CuSO4 → ZnSO4 + Cu.
