11. Which of the following compounds is used as an antacid?
- (a) Mg(OH)₂
- (b) Ca(OH)₂
- (c) NaOH
- (d) KOH
Answer: (a) Mg(OH)₂
Explanation: Magnesium hydroxide, also known as “milk of magnesia,” is used as an antacid because it neutralizes stomach acid without causing excessive alkalinity.
12. Which of the following elements does not show the diagonal relationship in the periodic table?
- (a) Li
- (b) Be
- (c) Na
- (d) Mg
Answer: (c) Na
Explanation: Sodium (Na) does not show a diagonal relationship with any element. The diagonal relationship is observed between lithium (Li) and magnesium (Mg), and between beryllium (Be) and aluminum (Al).
13. Which alkali metal forms the strongest base?
- (a) LiOH
- (b) NaOH
- (c) KOH
- (d) CsOH
Answer: (d) CsOH
Explanation: Cesium hydroxide (CsOH) is the strongest base among alkali metal hydroxides because the basicity increases as we move down the group due to the increasing ionic size and decreasing lattice energy.
14. Which alkaline earth metal is used in the preparation of cement?
- (a) Magnesium
- (b) Calcium
- (c) Barium
- (d) Strontium
Answer: (b) Calcium
Explanation: Calcium is a key element in the preparation of cement, specifically in the form of calcium carbonate (CaCO₃) and calcium silicates, which are used to form the clinker that is ground to make cement.
15. Which of the following elements forms superoxides?
- (a) Lithium
- (b) Sodium
- (c) Potassium
- (d) Rubidium
Answer: (d) Rubidium
Explanation: Heavier alkali metals like rubidium (Rb) and cesium (Cs) form superoxides (RbO₂ and CsO₂) due to their large ionic sizes, which stabilize the superoxide ion (O2−)(O2−). Potassium also forms superoxides under certain conditions.
16. Which of the following elements is the most electropositive?
- (a) Lithium
- (b) Sodium
- (c) Potassium
- (d) Cesium
Answer: (d) Cesium
Explanation: Cesium is the most electropositive element due to its large atomic size and low ionization energy, which makes it easier to lose an electron.
17. Which alkali metal forms the most stable chloride?
- (a) Lithium
- (b) Sodium
- (c) Potassium
- (d) Cesium
Answer: (b) Sodium
Explanation: Sodium chloride (NaCl) is the most stable chloride due to its optimal size ratio between Na⁺ and Cl⁻ ions, resulting in a stable ionic lattice with high lattice energy.
18. Which of the following elements shows a diagonal relationship with aluminum?
- (a) Lithium
- (b) Beryllium
- (c) Magnesium
- (d) Sodium
Answer: (b) Beryllium
Explanation: Beryllium (Be) shows a diagonal relationship with aluminum (Al). Both form covalent compounds, have amphoteric oxides, and their hydroxides dissolve in excess alkali to form beryllates and aluminates, respectively.
19. Which alkali metal carbonate is least stable thermally?
- (a) Li₂CO₃
- (b) Na₂CO₃
- (c) K₂CO₃
- (d) Cs₂CO₃
Answer: (a) Li₂CO₃
Explanation: Lithium carbonate (Li₂CO₃) is less stable than the carbonates of other alkali metals and decomposes at a lower temperature due to the small size of the lithium ion, which has a higher polarizing power, leading to the distortion of the carbonate ion.
20. Which alkaline earth metal hydroxide is most soluble in water?
- (a) Be(OH)₂
- (b) Mg(OH)₂
- (c) Ca(OH)₂
- (d) Ba(OH)₂
Answer: (d) Ba(OH)₂
Explanation: The solubility of alkaline earth metal hydroxides increases as we move down the group. Thus, barium hydroxide (Ba(OH)2)(Ba(OH)2) is the most soluble in water.
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