Vidaara.orgClass 11 · Chemistry
CodeVID-C11-10-CH-01
The s-Block Elements — Full Chapter 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 given; for full solutions, raise doubts with your teacher.
Section A — Multiple Choice Questions
6 × 1 = 6 marks
1.
The alkali metal giving a golden-yellow flame is:
- A.Li
- B.Na
- C.K
- D.Cs
2.
The strongest reducing agent in aqueous solution is:
- A.Na
- B.K
- C.Cs
- D.Li
3.
The amphoteric oxide is:
- A.Na2O
- B.MgO
- C.BeO
- D.CaO
4.
Washing soda is:
- A.NaHCO3
- B.Na2CO3·10H2O
- C.NaOH
- D.NaCl
5.
The metal ion at the centre of chlorophyll is:
- A.Ca2+
- B.Na+
- C.Mg2+
- D.K+
6.
Plaster of Paris is:
- A.CaSO4·2H2O
- B.CaSO4·½H2O
- C.CaCO3
- D.CaO
Section B — Short Answer (2 marks)
4 × 2 = 8 marks
7.
Why does ionisation enthalpy decrease down Group 1?
8.
Write the reaction occurring when CO2 is passed through lime water.
9.
Give two anomalies of beryllium.
10.
State the biological role of the sodium–potassium pump.
Section C — Long Answer (3 marks)
2 × 3 = 6 marks
11.
Explain three points of anomalous behaviour of lithium and link one of them to its diagonal relationship with magnesium.
12.
Describe the manufacture of sodium carbonate by the Solvay process with equations.
Section D — Detailed Answer (5 marks)
2 × 5 = 10 marks
13.
Compare the trends in atomic radius, ionisation enthalpy, hydration enthalpy and reactivity for Group 1 and Group 2, and explain why Group 2 metals are harder and less reactive.
14.
Discuss the biological importance of Na, K, Mg and Ca, naming where each is found and its function.
Answer Key
Section A — Multiple Choice Questions
- (B) Na
- (D) Li
- (C) BeO
- (B) Na2CO3·10H2O
- (C) Mg2+
- (B) CaSO4·½H2O
Section B — Short Answer (2 marks)
- Atomic size increases and shielding rises down the group, so the ns1 electron is held more loosely and is easier to remove.
- Ca(OH)2 + CO2 → CaCO3 (white, turns milky) + H2O; excess CO2 gives soluble Ca(HCO3)2.
- Its compounds (e.g. BeCl2) are covalent, and its oxide/hydroxide are amphoteric; it also does not react with water.
- It uses ATP to keep Na+ high outside and K+ high inside cells; the resulting gradients drive nerve impulses and fluid balance.
Section C — Long Answer (3 marks)
- Covalent character of its salts, sparingly soluble Li2CO3/LiF, and direct formation of Li3N. The nitride formation is shared with Mg (Mg3N2), illustrating the Li–Mg diagonal relationship.
- Saturate brine with NH3, pass CO2: NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl; filter and heat: 2NaHCO3 → Na2CO3 + H2O + CO2.
Section D — Detailed Answer (5 marks)
- Down both groups atomic radii increase while ionisation and hydration enthalpies decrease and reactivity increases. Group 2 atoms are smaller with higher nuclear charge and higher ionisation enthalpies than Group 1 of the same period. Two valence electrons give stronger metallic bonding (harder, higher melting), and the harder electron loss makes them less reactive than the alkali metals.
- Na+ (outside cells) and K+ (inside cells) maintain the gradients (via the Na–K pump) needed for nerve signals, fluid balance and nutrient transport. Mg2+ is the central ion of chlorophyll (photosynthesis) and activates ATP-using enzymes. Ca2+ builds bones and teeth (calcium phosphate/carbonate) and, in body fluids, is essential for blood clotting, muscle contraction and nerve transmission.
Generated by Vidaara.org · Assignment VID-C11-10-CH-01 · vidaara.org