Vidaara.orgClass 11 · Chemistry
CodeVID-C11-10-T2-01
Group 2: Alkaline Earth Metals — Assignment
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Show full working for Sections B, C and D; only final answers are provided.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
Alkaline earth metals belong to group:
- A.1
- B.2
- C.13
- D.17
2.
Which element does NOT impart colour to a flame?
- A.Ca
- B.Sr
- C.Ba
- D.Mg
3.
The amphoteric oxide among the following is:
- A.MgO
- B.CaO
- C.BeO
- D.BaO
4.
Gypsum is:
- A.CaSO4·½H2O
- B.CaSO4·2H2O
- C.CaCO3
- D.Ca(OH)2
5.
Slaked lime is:
- A.CaO
- B.CaCO3
- C.Ca(OH)2
- D.CaSO4
Section B — Short Answer (2 marks)
3 × 2 = 6 marks
6.
Why is BeCl2 covalent while MgCl2 is largely ionic?
7.
Write the reaction for the conversion of limestone to quicklime.
8.
Why is plaster of Paris stored in moisture-proof containers?
Section C — Long Answer (3 marks)
2 × 3 = 6 marks
9.
Explain the diagonal relationship between beryllium and aluminium with three examples.
10.
Describe the preparation, setting and two uses of plaster of Paris.
Section D — Detailed Answer (5 marks)
1 × 5 = 5 marks
11.
Compare the general characteristics and trends of Group 2 metals with Group 1, and explain why Group 2 metals are harder and less reactive than the corresponding Group 1 metals.
Answer Key
Section A — Multiple Choice Questions
- (B) 2
- (D) Mg
- (C) BeO
- (B) CaSO4·2H2O
- (C) Ca(OH)2
Section B — Short Answer (2 marks)
- Be2+ is very small with high polarising power; it distorts the chloride electron cloud strongly (Fajans' rules), giving covalent character, whereas the larger Mg2+ polarises less.
- CaCO3 → CaO + CO2 (on strong heating / calcination).
- It absorbs water and sets to a hard mass of gypsum (CaSO4·2H2O), so contact with moisture would spoil it before use.
Section C — Long Answer (3 marks)
- Similar charge-to-radius ratio leads to: amphoteric oxides (BeO, Al2O3); covalent chlorides that are Lewis acids (BeCl2, AlCl3); and dissolution of both metals in alkali with evolution of hydrogen.
- Preparation: 2CaSO4·2H2O → 2CaSO4·½H2O + 3H2O (heating gypsum at ~393 K). Setting: it reabsorbs water to re-form gypsum, expanding slightly to fill moulds. Uses: plaster casts for fractures and making moulds/statues.
Section D — Detailed Answer (5 marks)
- Group 2 (ns2, +2 ions) are smaller, harder, denser and higher-melting than Group 1 (ns1, +1) of the same period. Down each group radii increase and ionisation enthalpy/reactivity follow opposite-but-parallel trends. Group 2 metals are harder because two valence electrons give stronger metallic bonding, and less reactive because their higher nuclear charge and higher ionisation enthalpies make electron loss harder than for the alkali metals.
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