Answer :Grinding mill (such as a Ball mill or Stamp mill).
5. The nonmetal having electrical conductivity.
Answer :Graphite (an allotropic form of carbon with delocalized free electrons).
6. The reagent that dissolves noble metals.
Answer :Aqua regia (a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in a 3 : 1 ratio by volume).
Q2)Make pairs of substances and their properties.
The given substances matched with their correct chemical and physical properties:
Substance (Column I)
Property (Column II)
(1) Potassium bromide
Soluble in water (Ionic compound forming hydrated ions)
(2) Gold
High ductility (Can be drawn into extremely thin wires)
(3) Sulphur
Combustible (Burns easily in air to form sulfur dioxide)
(4) Neon
No chemical reaction (Inert noble gas with completed octet)
Q3)Identify the pairs of metals and their ores from the following.
The correct matching pairs of ores and their corresponding primary metals:
Ore (Column I)
Metal (Column II)
(1) Bauxite (Al₂O₃ · 2H₂O)
Aluminium (Al)
(2) Cassiterite (SnO₂)
Tin (Sn)
(3) Cinnabar (HgS)
Mercury (Hg)
Q4)Explain the terms:
1. Metallurgy
Answer :Metallurgy is the entire sequence of scientific and technological processes employed to extract metals in their pure form from their natural ores, followed by their refining and conditioning for practical commercial applications.
2. Ores
Answer :Ores are naturally occurring minerals from which metals can be extracted profitably, economically, and conveniently. For instance, Bauxite (Al₂O₃ · 2H₂O) is the ore of aluminium, and Cinnabar (HgS) is the ore of mercury.
3. Minerals
Answer :Minerals are naturally occurring inorganic substances found in the Earth's crust that contain metal compounds combined with other natural elements and earthy compounds.
4. Gangue
Answer :Gangue refers to the unwanted earthy, sandy, and rocky impurities (such as sand, clay, limestone, and soil) naturally associated with mined metallic ores before concentration.
Q5)Write scientific reasons:
1. Lemon or tamarind is used for cleaning copper vessels turned greenish.
Answer :
Copper reacts slowly with moist air and carbon dioxide to form a green layer of basic copper carbonate [CuCO₃ · Cu(OH)₂].
Lemon and tamarind contain mild acids (citric acid in lemon and tartaric acid in tamarind).
These acids react with the basic green layer and dissolve it into water-soluble copper salts.
When washed with water, the green coating is removed, restoring the reddish-brown shine of the copper vessel.
2. Generally the ionic compounds have high melting points.
Answer :
Ionic compounds are made of oppositely charged positive and negative ions.
These ions are held together by very strong electrostatic forces of attraction.
A large amount of heat energy is needed to break these strong bonds.
Hence, ionic compounds have very high melting and boiling points.
3. Sodium is always kept in kerosene.
Answer :
Sodium is a very reactive metal that catches fire easily when exposed to air and moisture at room temperature.
Sodium does not react with kerosene and sinks in it.
Keeping sodium in kerosene cuts off its contact with air and moisture, keeping it completely safe from catching fire.
4. Pine oil is used in the froth floatation process.
Answer :
In the froth floatation method, sulfide ore particles are wetted by pine oil, while gangue (impurities) are wetted by water.
When air is blown through the mixture, pine oil creates a light foam (froth) that floats to the top carrying the sulfide ore particles with it.
The water-wetted gangue particles sink to the bottom, allowing the ore to be easily separated and concentrated.
5. Anodes need to be replaced from time to time during the electrolysis of alumina.
Answer :
During the electrolytic reduction of molten alumina (Al₂O₃), oxygen gas (O₂) is discharged at the positive carbon (graphite) anodes: 2O²⁻ → O₂ + 4e⁻.
At the high cell operating temperature (around 950°C–1000°C), this liberated oxygen reacts chemically with the graphite anodes to form carbon dioxide gas: C(s) + O₂(g) → CO₂(g)↑.
Because the carbon anodes undergo continuous burning/oxidation and erosion, their mass decreases steadily, making regular periodic replacement necessary.
Q6)When a copper coin is dipped in silver nitrate solution, a glitter appears on the coin after some time. Why does this happen? Write the chemical equation.
Answer :
In the reactivity series of metals, copper (Cu) is more electropositive and reactive than silver (Ag). When a copper coin is dipped into an aqueous solution of silver nitrate (AgNO₃), copper displaces silver ions from the solution through a single displacement reaction.
The displaced metallic silver gets deposited as a shining, lustrous coating over the surface of the copper coin, giving it a bright glitter. Concurrently, copper dissolves into the solution forming copper(II) nitrate, imparting a faint blue tint to the liquid.
Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)↓
Q7)The electronic configuration of metal 'A' is 2, 8, 1 and that of metal 'B' is 2, 8, 2. Which of the two metals is more reactive? Identify these metals. Write their reaction with dilute hydrochloric acid.
Answer :
Identification of Metals:
Metal ‘A’ has atomic number 2 + 8 + 1 = 11, which corresponds to Sodium (Na).
Metal ‘B’ has atomic number 2 + 8 + 2 = 12, which corresponds to Magnesium (Mg).
Comparison of Reactivity:
Metal ‘A’ (Sodium) has only 1 valence electron, whereas Metal ‘B’ (Magnesium) has 2 valence electrons. Because losing 1 electron requires far less ionization energy than losing 2 electrons, sodium loses its valence electron much more readily to attain a stable octet. Hence, Metal ‘A’ (Sodium) is more reactive than Metal ‘B’ (Magnesium).
Reactions with Dilute Hydrochloric Acid (HCl):
Reaction of Metal A (Sodium):
2Na(s) + 2HCl(aq) → 2NaCl(aq) + H₂(g)↑
(Reacts explosively and vigorously, liberating hydrogen gas and sodium chloride).
Reaction of Metal B (Magnesium):
Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)↑
(Reacts vigorously with brisk effervescence of hydrogen gas and forms magnesium chloride).
Q8)Draw a neat labelled diagram.
1. Magnetic separation method
Answer :
Fig 8.1: Magnetic Separation Method
2. Froth floatation method
Answer :
Fig 8.2: Froth Floatation Method
3. Electrolytic reduction of alumina
Answer :
Fig 8.3: Electrolytic Reduction of Alumina (Hall-Héroult Process)
Q9)Write chemical equation for the following events:
1. Aluminium came in contact with air.
Answer :
When aluminium is exposed to atmospheric oxygen, it readily reacts to form an extremely thin, protective, and non-porous layer of aluminium oxide (Al₂O₃) on its surface, which prevents deeper corrosion.
4Al(s) + 3O₂(g) → 2Al₂O₃(s)
2. Iron filings are dropped in aqueous solution of copper sulphate.
Answer :
Iron (Fe) is more reactive than copper (Cu) and displaces copper from copper sulphate solution. The characteristic blue color of copper sulphate fades to light pale green due to the formation of ferrous sulphate, and reddish-brown copper deposits on the iron filings.
Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)↓
3. A reaction was brought about between ferric oxide and aluminium.
Answer :
This is the highly exothermic Thermite reaction. Aluminium acts as a powerful reducing agent, reducing ferric oxide to molten metallic iron while liberating tremendous heat.
Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat
(The molten iron produced is used in thermite welding of cracked railway tracks and heavy machinery).
4. Electrolysis of alumina is done.
Answer :
In the electrolytic cell, molten alumina undergoes decomposition into pure molten aluminium at the cathode and oxygen gas at the anode:
Cathode reaction (Reduction):
Al³⁺ + 3e⁻ → Al(l)
Anode reaction (Oxidation):
2O²⁻ → O₂(g) + 4e⁻
Overall cell reaction:
2Al₂O₃(l) → 4Al(l) + 3O₂(g)↑
The released oxygen also reacts with the carbon anodes: C(s) + O₂(g) → CO₂(g)↑.
5. Zinc oxide is dissolved in dilute hydrochloric acid.
Answer :
Zinc oxide (ZnO) is an amphoteric oxide that acts as a basic oxide when reacting with dilute hydrochloric acid, neutralizing it to form soluble zinc chloride and water.
ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l)
Q10)Complete the following statement using every given options. During the extraction of aluminium:
Answer :
The extraction of pure aluminium from bauxite ore involves chemical concentration (leaching) followed by electrolytic reduction, incorporating each given aspect:
Ingredients and gangue in bauxite:
Bauxite (Al₂O₃ · 2H₂O) is the principal ore of aluminium. The major gangue impurities present in bauxite are silica (SiO₂), ferric oxide (Fe₂O₃), and titanium dioxide (TiO₂).
Use of leaching during the concentration of ore:
Because bauxite ore contains both acidic (SiO₂) and basic (Fe₂O₃) gangue, physical separation methods are ineffective. Hence, chemical separation by leaching (Bayer’s process or Hall’s process) is employed to dissolve alumina selectively while leaving impurities behind.
Heating the aluminium ore with concentrated caustic soda (Bayer’s Process):
Powdered bauxite is digested with concentrated aqueous caustic soda (NaOH) at 140°C–150°C under 2–8 atm pressure for 2 to 8 hours. Being amphoteric, alumina dissolves as water-soluble sodium aluminate, whereas ferric oxide gangue remains insoluble and is filtered out:
The resulting sodium aluminate filtrate is warmed to 50°C and neutralized by bubbling carbon dioxide (CO₂) gas, precipitating pure aluminium hydroxide:
Class 10 Maharashtra State Board Science Part 1 Chapter 8 covers the physical and chemical properties of metals and nonmetals, the reactivity series, corrosion, and extraction techniques. Key concepts include concentration of ores (hydraulic separation, magnetic separation, froth floatation, leaching), roasting, calcination, Bayer's and Hall's process for alumina, and the Hall-Héroult electrolytic reduction.
Frequently Asked Questions (FAQs)
Q1. What is the difference between an ore and a mineral?
A mineral is any naturally occurring compound of a metal found in the Earth's crust. An ore is a specific mineral from which the metal can be extracted profitably, easily, and economically. All ores are minerals, but all minerals are not ores.
Q2. Why is cryolite added to alumina during the Hall-Héroult process?
Pure alumina has an extremely high melting point (over 2000°C) and is a poor electrical conductor. Adding cryolite (Na₃AlF₆) and fluorspar (CaF₂) lowers the melting point to approximately 950°C–1000°C and greatly increases its electrical conductivity.
Q3. What is aqua regia?
Aqua regia is a highly corrosive fuming mixture consisting of 3 parts concentrated hydrochloric acid (HCl) and 1 part concentrated nitric acid (HNO₃) by volume. It can dissolve noble metals such as gold and platinum.
Q4. How does froth floatation separate sulfide ores?
Sulfide ore particles are wetted by pine oil and cling to rising air bubbles to form surface froth, while unwanted gangue particles are wetted by water and sink to the bottom.
Related Study Topics
Metallurgy Class 10Froth Floatation ProcessExtraction of AluminiumBayer's ProcessHall-Heroult MethodThermite ReactionReactivity SeriesSSC Board Science 1