12th Chemistry _Ch 17_Long Questions (Group 2 Elements) New Book 2026

Overview

Ye Long Questions poore chapter ke concepts ko detailed, exam-style tareeqe se explain karte hain. Har question mein ek bara topic cover hota hai — properties, reactivity, thermal stability, solubility, complexes, extraction, aur uses. In sab mein ek hi bunyadi idea baar baar ghumti hai: jaise jaise group mein neeche jaate hain (Be→Ba), size barhta hai — aur isi se sab trends nikalte hain.

Long Question 1 — Group 2 Elements Ki Properties Aur Trends

Ye ek overview-type sawal hai jisme sab basic trends ek jaga collect kiye gaye hain:

Electron Configuration: Sab Group 2 elements ka outer configuration ns² hota hai (jaise Ca: [Ar]4s²). Chunke sab do electrons khokar M²⁺ ion banate hain, isliye chemical behaviour poore group mein similar hota hai.

Atomic/Ionic Radius: Dono size (metallic aur ionic) group mein neeche jaate hue barhte hain, kyunke har element mein ek naya electron shell add hota hai (Be:112pm → Ba:222pm).

Ionization Energy: Pehli aur dusri dono ionization energies group mein neeche jaate hue kam hoti hain — wajah: size barhne se aur andar ke electrons ki shielding barhne se, outer electrons par nucleus ka kheenchav kamzor ho jata hai.

Electronegativity aur Electrode Potential: Electronegativity kam hoti hai neeche jaate hue, aur standard electrode potential zyada negative ho jata hai — matlab metal ki electron chhodne ki tendency barh jaati hai (reducing agent ki tarah behaviour barh jata hai).

Melting Point aur Density: Melting point generally kam hota hai (Be sabse zyada). Density ka trend irregular hai — pehle Be se Ca tak kam hoti hai, phir Sr, Ba ke liye dobara barh jaati hai (kyunke mass, volume ke increase se zyada hawi ho jata hai).

Reactivity Trend: Reactivity barhti hai neeche jaate hue (Be<Mg<Ca<Sr<Ba) — kyunke size barhta hai, shielding barhti hai, aur ionization energy kam hoti hai, jisse do valence electrons nikalna aasan ho jata hai.

Yaad rakhne ka tareeqa: Bas ek trend yaad karo — size barhta hai, ionization energy kam hoti hai — baaki sab isi se derive ho jata hai.

Long Question 2 — Oxygen, Water, Aur Acids Ke Saath Reactivity

Oxygen Ke Saath:

• Sab metals jal kar oxide banate hain: 2M + O₂ → 2MO
• Be sirf 600°C se upar react karta hai (protective BeO layer ki wajah se)
• Mg brightly jalta hai, Ca aur zyada vigorously, brick-red flame ke saath
• Oxides basic aur white solid hote hain; basic character neeche jaate hue barhta hai

Water Ke Saath:

• Be paani/steam se bilkul react nahi karta (protective oxide layer)
• Mg cold water se bohot dheere react karta hai (Mg(OH)₂+H₂), steam se tezi se (MgO+H₂)
• Ca, Mg se zyada vigorously react karta hai; Ca(OH)₂ sparingly soluble hai, isliye white precipitate ki soorat mein nazar aata hai

Acids Ke Saath:

• Sab: M+2HCl → MCl₂+H₂
• Be dheere react karta hai (pehle oxide layer todni parti hai)
• Mg aasani se react karta hai
• Ca dilute HCl se vigorously react karta hai, lekin dilute H₂SO₄ ke saath reaction jaldi ruk jata hai kyunke CaSO₄ sparingly soluble hai aur metal surface par coating ban jaati hai jo aage reaction rokti hai

Overall Trend: Teeno reactions (oxygen, water, acid) mein reactivity Be se Ca (aur aage Ba tak) barhti hai — ionization energy kam hone aur size barhne ki wajah se.

Long Question 3 — Reactivity Series Ka Concept

Definition: Reactivity series metals ko unki reactivity ke hisaab se order mein arrange karti hai (most reactive se least reactive). Group 2 ke liye order: Be < Mg < Ca < Sr < Ba

Is Series Ki Bunyad: Ye order ionization energy kam hone aur size barhne par based hai — jitna aasan hoga do electrons nikalna, utni zyada reactivity.

Reaction Outcomes Predict Karna: Ye series batati hai ke koi metal kitni vigorously react karega, ya karega bhi ya nahi. Jaise: Be series mein sabse neeche hai, isliye predict hota hai (aur observe bhi hota hai) ke ye cold water/steam se react nahi karega, jabke Ca zyada reactive hone ki wajah se vigorously react karega.

Group 1 Se Comparison: Group 1 metals ka sirf ek valence electron hota hai aur unki ionization energy bohot kam hoti hai, isliye wo Group 2 se zyada reactive hote hain (jaise sodium paani se explosively react karta hai, jabke same period ka Group 2 metal utna vigorously nahi karta). Wajah simple hai: Group 1 ko sirf ek electron nikalna hai (kam energy cost), Group 2 ko do electrons (zyada combined ionization energy).

Long Question 4 — Group 2 Vs Group 1 Comparison

Ye ek table-type comparison hai, jise points mein yaad karna aasan hai:

Wajah: Group 1 mein sirf ek delocalized electron per atom hota hai, isliye metallic bonding kamzor hoti hai (isliye naram, kam density). Group 2 mein har atom do electrons deta hai, isliye bonding mazboot hoti hai.

Long Question 5 — Carbonates Aur Nitrates Ki Thermal Decomposition

Definition: Thermal decomposition ek reaction hai jisme heat lagane se ek compound do ya zyada simpler substances mein toot jata hai. Ye hamesha endothermic hoti hai (bonds todne ke liye energy chahiye).

Carbonates: MCO₃(s) → MO(s) + CO₂(g)
Misaal: CaCO₃(s) → CaO(s) + CO₂(g)

Nitrates: 2M(NO₃)₂(s) → 2MO(s) + 4NO₂(g) + O₂(g)
Misaal: 2Ca(NO₃)₂(s) → 2CaO(s) + 4NO₂(g) + O₂(g)

Trend Ki Wajah — Polarizing Power:

• Thermal stability M²⁺ cation ki size aur charge density (polarizing power) par depend karti hai
• Chote, zyada charged cations (jaise Be²⁺) anion ko zyada distort karte hain, jisse bond kamzor ho jata hai, aur compound kam temperature par hi decompose ho jata hai
• Cation size barhne se polarizing power kam hoti hai, isliye compound zyada stable ho jata hai (zyada temperature chahiye decompose hone ke liye)

Order (barhti stability):

BeCO3(250°C)<MgCO3(540°C)<CaCO3(900°C)<SrCO3(1289°C)<BaCO3(1360°C)BeCO_3 (250°C) < MgCO_3 (540°C) < CaCO_3 (900°C) < SrCO_3 (1289°C) < BaCO_3 (1360°C)BeCO3​(250°C)<MgCO3​(540°C)<CaCO3​(900°C)<SrCO3​(1289°C)<BaCO3​(1360°C)

Same order nitrates ke liye bhi hai.

Application: Decomposition temperature dekh kar unknown compound identify kiya ja sakta hai, aur ionic size, charge density, aur thermal stability ka rishta samjha ja sakta hai.

Long Question 6 — Sulphates Aur Hydroxides Ki Solubility

Do Bunyadi Energy Terms:

1. Enthalpy of hydration (∆H_hyd): Jab gaseous ions paani ke molecules se gher liye jate hain to energy release hoti hai (exothermic). Ion size barhne se ye kam negative hoti jaati hai.
2. Lattice enthalpy (∆H_lattice): Solid compound ko gaseous ions mein todne ke liye energy chahiye (endothermic).

Enthalpy of Solution (∆H_soln): Ye dono ka sum hai. Jitna zyada negative (ya kam positive) ye ho, utni zyada solubility.

Hydroxides: Solubility barhti hai neeche jaate hue (Mg(OH)₂ kam soluble → Ba(OH)₂ zyada soluble)

• Wajah: OH⁻ ion chota hai, isliye cation bara hone par lattice enthalpy zyada tezi se girti hai hydration enthalpy ke muqablay mein → dissolution zyada favourable ho jata hai

Sulphates: Solubility ghatti hai neeche jaate hue (MgSO₄ soluble → BaSO₄ tقریبا insoluble)

• Wajah: SO₄²⁻ ion bara hai, isliye cation bara hone par hydration enthalpy zyada tezi se girti hai lattice enthalpy ke muqablay mein → dissolution kam favourable hota jata hai

Comparative Data (experimental proof):

• Mg(OH)₂ → Ba(OH)₂: solubility barhti hai
• MgSO₄ → BaSO₄: solubility ghatti hai

Nateeja: Dono trends ulte isliye hain kyunke anion ka size (chota OH⁻ vs bara SO₄²⁻) decide karta hai ke lattice enthalpy hawi hogi ya hydration enthalpy.

Long Question 7 — Complex Ion Aur Group 2 Compounds

Complex Ion Ki Definition: Ye ek ion hai jisme ek central metal ion, kai electron-donating species (ligands) se coordinate (dative) bonds ke zariye juda hota hai. Metal ion Lewis acid (electron pair acceptor) ki tarah kaam karta hai, aur ligands Lewis base (electron pair donor) hote hain. Kitne coordinate bonds bante hain, ise coordination number kehte hain (common values: 2, 4, 6).

Group 2 Mein Complex Formation: Ye transition metals mein zyada common hai (d-orbitals ki wajah se), lekin Group 2 elements bhi bana sakte hain — khaas kar group ke upar wale (chote) elements. Chote ions ki charge density zyada hoti hai, isliye wo electron-donating species ko behtar attract karte hain.

Hydrated Complex Ions: Jab Group 2 salts paani mein ghulte hain, metal ions hydrated ho jate hain — paani ke molecules ligands ki tarah kaam karte hain:

• Be (sabse chota, sabse zyada charge density): [Be(H₂O)₄]²⁺ (coordination number 4)
• Mg: [Mg(H₂O)₆]²⁺ (coordination number 6)
• Ca, Sr, Ba: bhi coordination number 6 wale hydrated ions banate hain, lekin interaction ki strength neeche jaate hue kam hoti hai

Multidentate Ligands Ke Saath Complexes: Chote ions ring-like structures bhi bana sakte hain multi-electron-pair-donor ligands ke saath, jaise EDTA (6 electron pairs deta hai):

Ca2+(aq)+EDTA4−(aq)→[Ca(EDTA)]2−(aq)Ca^{2+}(aq) + EDTA^{4-}(aq) \rightarrow [Ca(EDTA)]^{2-}(aq)Ca2+(aq)+EDTA4−(aq)→[Ca(EDTA)]2−(aq)

Application: Ye complex formation water softening mein use hoti hai — EDTA hard water se Ca²⁺ aur Mg²⁺ ions nikal deta hai. Medically bhi EDTA se toxic metal ions (aur zyada calcium) jism se nikale ja sakte hain.

Long Question 8 — Extraction Aur Purification (Dow Process Aur Quicklime)

Dow Process (Magnesium Ki Extraction Seawater Se):

Step 1 — Precipitation: Ca(OH)₂ milaya jata hai seawater mein:

Mg2+(aq)+Ca(OH)2(s)→Mg(OH)2(s)+Ca2+(aq)Mg^{2+}(aq) + Ca(OH)_2(s) \rightarrow Mg(OH)_2(s) + Ca^{2+}(aq)Mg2+(aq)+Ca(OH)2​(s)→Mg(OH)2​(s)+Ca2+(aq)

Step 2 — Chloride mein convert karna: Mg(OH)₂ ko HCl ke saath react karaya:

Mg(OH)2(s)+2HCl(aq)→MgCl2(aq)+2H2O(l)Mg(OH)_2(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + 2H_2O(l)Mg(OH)2​(s)+2HCl(aq)→MgCl2​(aq)+2H2​O(l)

Step 3 — Concentration, Drying, Aur Electrolysis: MgCl₂ ko concentrate/dry kiya, phir molten MgCl₂ ko electrolyse kiya:

MgCl2(l)→Mg(l)+Cl2(g)MgCl_2(l) \rightarrow Mg(l) + Cl_2(g)MgCl2​(l)→Mg(l)+Cl2​(g)

Cathode par Mg, anode par Cl₂

Quicklime (CaO) Ka Production Limestone Se:

• Limestone (CaCO₃) ko lime kiln mein 900-1000°C par heat kiya jata hai (calcination):
  CaCO3(s)→heatCaO(s)+CO2(g)CaCO_3(s) \xrightarrow{heat} CaO(s) + CO_2(g)CaCO3​(s)heat​CaO(s)+CO2​(g)
• Equilibrium shift karna: Chunke ye reaction reversible hai, CO₂ ko musalsal hataya jata hai, jisse Le Chatelier’s principle ke mutabiq equilibrium right ki taraf shift ho jaati hai, aur zyada quicklime bante hai

Significance: Quicklime construction, agriculture, aur metallurgy mein use hoti hai — ye sabse purani aur bunyadi industrial processes mein se ek hai.

Long Question 9 — Group 2 Compounds Ke Industrial Aur Everyday Uses

Ye ek applications-based sawal hai, categories mein yaad karo:

Construction:

• CaCO₃ (limestone/marble/chalk) → building material, cement, filler
• CaO/Ca(OH)₂ → cement, mortar, plaster; quicklime steel banane mein bhi use hoti hai
• CaSO₄·2H₂O (gypsum) → plasterboard aur Plaster of Paris

Environment:

• CaO/CaCO₃ → flue gas desulphurization (power plants se SO₂ hatana, acid rain rokna)
• MgO → furnace lining (refractory material, high melting point ki wajah se)

Industrial:

• Mg → lightweight alloys (aerospace, automotive), fireworks/flares
• Strontium → fireworks mein laal color
• Beryllium → alloys mein strength barhata hai (springs, aerospace), X-ray tubes (X-rays ke liye transparent hai)

Medicine:

• Mg(OH)₂ (Milk of Magnesia) → antacid aur laxative
• CaCO₃ → indigestion tablets
• Calcium compounds → bones/teeth ke liye supplements (osteoporosis rokne ke liye)
• Mg compounds → muscle/nerve function ke liye
• Epsom salts (MgSO₄·7H₂O) → laxative aur therapeutic baths
• BaSO₄ → barium meal (X-ray imaging)

Agriculture:

• CaCO₃/Ca(OH)₂ → acidic soil neutralize karne ke liye
• Calcium → cell wall development, Magnesium → chlorophyll ka central atom (photosynthesis ke liye zaroori)
• Calcium nitrate, Epsom salts → fertilizers

Sabse Zaroori Baat (Exam Ke Liye):

Long questions mein examiner balanced equations aur exact reasoning (jaise “polarizing power”, “hydration enthalpy vs lattice enthalpy”) dekhta hai. Har jawab mein pehle concept/definition, phir reason/mechanism, aur aakhir mein trend/example likhna best strategy hai — isi tarteeb se marks milte hain.