Std 10th Science Part 1 – Chapter 8 : Metallurgy Exercise Questions And Answers Maharashtra Board

Q1. Write names. 

a. Alloy of sodium with mercury

Answer – Silver Amalgam.

b. Molecular formula of the common ore of aluminium.

Answer – Al₂​O₃​⋅nH₂​O (Bauxite) 

c. The oxide that forms salt and water by reacting with both acid and base.

Answer – Aluminium oxide (Al₂​O_3​)

d. The device used for grinding an ore.

Answer – Grinding mill 

e. The nonmetal having electrical conductivity.

Answer – Graphite (an allotrope of carbon)

f. The reagent that dissolves noble metals.

Answer – Aqua Regia

Q2. Make pairs of substances and their properties

Substance	Property
a. Potassium bromide (KBr)	1. Combustible
b. Gold (Au)	2. Soluble in water
c. Sulphur (S)	3. No chemical reaction
d. Neon (Ne)	4. High ductility

Answer – 

Substance	Property
a. Potassium bromide (KBr)	2. Soluble in water
b. Gold (Au)	4. High ductility
c. Sulphur (S)	1. Combustible
d. Neon (Ne)	3. No chemical reaction

Q3. Identify the pairs of metals and their ores from the following.

(Group A)	(Group B)
a. Bauxite	i. Mercury
b. Cassiterite	ii. Aluminium
c. Cinnabar	iii. Tin

Answer – 

(Group A)	(Group B)
a. Bauxite	ii. Aluminium
b. Cassiterite	iii. Tin
c. Cinnabar	i. Mercury

Q4. Explain the terms.

a. Metallurgy

Answer – It is the science and technology concerned with extracting metals from their ores and purifying them for use.

b. Ores

Answer – 

• These are the minerals from which a metal can be
  separated economically.
• Ores contain the metal compounds along with various impurities. 

c. Minerals

Answer – 

• These are the compounds of metals that occur naturally in the Earth’s crust, along with various impurities.

d. Gangue

Answer – These are the impurities such as soil, sand, and rocky substances found along with the metal compounds in the ores.

Q5. Write scientific reasons.

a. Lemon or tamarind is used for cleaning copper vessels turned greenish.

Answer – 

• When copper vessels are exposed to moist air for a long time, a greenish layer of copper carbonate (CuCO₃​) forms on their surface.
• Copper carbonate is a basic salt. Lemon or tamarind contains citric or tartaric acid, which are organic acids.
• The acid reacts with the basic copper carbonate to form a soluble salt, which can be easily washed away, restoring the copper’s shine.

b. Generally the ionic compounds have high melting points.

Answer –

• Ionic compounds are formed from positively charged
  cations and negatively charged anions.
• The electrostatic force of attraction (ionic bond) between these oppositely charged ions is very strong.
• A large amount of energy (heat) is required to overcome these strong intermolecular attractive forces and break the crystal lattice, thus resulting in high melting points. 

c. Sodium is always kept in kerosene.

Answer – 

• Sodium (Na) is a highly reactive metal.
• It combines with oxygen in the air even at room temperature, readily catching fire.
• To prevent this accidental reaction/fire, sodium is stored in kerosene to keep it isolated from air and moisture. 

d. Pine oil is used in froth flotation.

Answer – 

• The froth flotation method separates metal sulfide particles from gangue based on two properties: hydrophilic (water-attracting) and hydrophobic (water-repelling).
• Pine oil is used because it has a hydrophobic property, meaning it preferentially wets the metal sulfide particles.
• This makes the ore particles cling to the oil/air bubbles (froth) and float to the surface for collection.

e. Anodes need to be replaced from time to time during the electrolysis of alumina.

Answer – 

• During the electrolytic reduction of alumina (Al₂​O_3​) to extract aluminium, oxygen gas (O₂​) is liberated at the graphite anodes.
• This liberated oxygen reacts with the hot carbon (graphite) of the anodes to form carbon dioxide gas (CO₂​).
• Since the anode material is continuously consumed (oxidized), the graphite anodes need to be replaced periodically.

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 – 

• This happens because a displacement reaction takes place.
• Copper (Cu) is more reactive than silver (Ag). Copper displaces silver from its salt solution (silver nitrate).
• The displaced silver metal is deposited on the copper coin, causing a glitter to appear.
• Chemical Equation:

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? Write their reaction with dilute hydrochloric acid.

Answer – 

• More Reactive Metal:Metal ‘A’ (2, 8, 1) is more reactive.
  • Reason: Metal ‘A’ (Na) has one valence electron and is in Group 1. Metal ‘B’ (Mg) has two valence electrons and is in Group 2.
  • Reactivity in metals is the tendency to lose electrons easily. Losing one electron (as in ‘A’) is easier than losing two electrons (as in ‘B’). Thus, ‘A’ is more electropositive and more reactive.
• Reaction with dilute Hydrochloric Acid (HCl): (Note: Metal ‘A’ is likely Sodium (Na) and Metal ‘B’ is likely Magnesium (Mg))
  • Metal ‘A’ (Na): Reacts vigorously, but typically shown with water/oxygen as it’s highly reactive. However, assuming it reacts with dilute acid:

Q8. Draw a neat labelled diagram.

a. Magnetic separation method.

b. Froth floatation method.

c. Electrolytic reduction of alumina.

d. Hydraulic separation method.

Q9. Write chemical equation for the following events. 

a. Aluminium came in contact with air.

Answer – Aluminium is readily oxidized by oxygen in the air to form a thin layer of aluminium oxide.

4Al(s)+3O₂​(g)⟶2Al₂​O₃​(s)

b. Iron filings are dropped in aqueous solution of copper sulphate.

Answer – Iron, being more reactive than copper, displaces it (displacement reaction).

Fe(s)+CuSO₄​(aq)⟶FeSO₄​(aq)+Cu(s)

c. A reaction was brought about between ferric oxide (Fe_2​O₃​) and aluminium (Thermit Reaction).

Answer – Aluminium, being highly reactive, acts as a strong reducing agent to displace iron.

Fe₂​O₃​(s)+2Al(s)⟶2Fe(l)+Al_2​O₃​(s)+Heat

d. Electrolysis of alumina (Al2​O3​) is done.

Answer – 

• Cathode (Reduction): Aluminium ion gains electrons to become molten aluminium.
  Al³⁺+3e⁻⟶Al(l)
• Anode (Oxidation): Oxygen ion loses electrons to become oxygen gas.
  2O²⁻⟶O2​(g)+4e⁻

e. Zinc oxide is dissolved in dilute hydrochloric acid.

Answer – Zinc oxide (ZnO) is an amphoteric oxide and reacts with acid to form salt and water.

ZnO(s)+2HCl(aq)⟶ZnCl_2​(aq)+H₂​O(l)

Q10. Complete the following statement using every given options. 

During the extraction of aluminium………….. 

a.Ingredients and gangue in bauxite.

b.Use of leaching during the concentration of ore.

c.Chemical reaction of transformation of bauxite into alumina by Hall’s process.

d.Heating the aluminium ore with concentrated caustic soda.

Answer – c.Chemical reaction of transformation of bauxite into alumina by Hall’s process.

Q11. Divide the metals Cu, Zn, Ca, Mg, Fe, Na, Li into three groups, namely reactive metals, moderately reactive metals and less reactive metals.

Answer – 

Group	Metals
Highly Reactive Metals	Na (Sodium), Li (Lithium), Ca (Calcium)
Moderately Reactive Metals	Mg (Magnesium), Zn (Zinc), Fe (Iron)
Less Reactive Metals	Cu (Copper)