31. Which of the following elements forms a soluble sulfate?
- (a) Beryllium
- (b) Magnesium
- (c) Calcium
- (d) Barium
Answer: (b) Magnesium
Explanation: Magnesium sulfate (MgSO₄), also known as Epsom salt, is soluble in water, while the solubility of other alkaline earth metal sulfates decreases down the group.
32. Which of the following alkaline earth metals has the lowest first ionization energy?
- (a) Beryllium
- (b) Magnesium
- (c) Calcium
- (d) Barium
Answer: (d) Barium
Explanation: The first ionization energy decreases down the group for alkaline earth metals. Barium, being the heaviest element, has the lowest first ionization energy.
33. Which of the following alkaline earth metal oxides is most basic?
- (a) BeO
- (b) MgO
- (c) CaO
- (d) BaO
Answer: (d) BaO
Explanation: Basicity increases as we move down the group in alkaline earth metal oxides. Barium oxide (BaO) is the most basic because of the larger size of the Ba²⁺ ion.
34. Which of the following compounds is a component of baking powder?
- (a) K₂CO₃
- (b) NaHCO₃
- (c) Na₂CO₃
- (d) CaCO₃
Answer: (b) NaHCO₃
Explanation: Sodium bicarbonate (NaHCO₃) is a key ingredient in baking powder. It releases carbon dioxide when heated or in the presence of acid, causing dough to rise.
35. Which of the following elements forms the most soluble nitrate?
- (a) Magnesium
- (b) Barium
- (c) Calcium
- (d) Sodium
Answer: (d) Sodium
Explanation: Sodium nitrate (NaNO₃) is highly soluble in water, whereas the solubility of nitrates of alkaline earth metals decreases down the group.
36. Which of the following alkaline earth metals is used in medicine to treat osteoporosis?
- (a) Calcium
- (b) Magnesium
- (c) Strontium
- (d) Beryllium
Answer: (c) Strontium
Explanation: Strontium ranelate is used in the treatment of osteoporosis, a condition that weakens bones, making them fragile and more likely to break.
37. Which of the following compounds is used in the purification of bauxite ore in the Bayer process?
- (a) NaOH
- (b) KOH
- (c) CaO
- (d) MgO
Answer: (a) NaOH
Explanation: Sodium hydroxide (NaOH) is used in the Bayer process to purify bauxite ore. It dissolves the alumina (Al₂O₃) to form soluble sodium aluminate, leaving behind the impurities.
38. Which of the following is the correct order of atomic radii for alkali metals?
- (a) Li > Na > K > Rb
- (b) Na > Li > K > Rb
- (c) Rb > K > Na > Li
- (d) K > Na > Li > Rb
Answer: (c) Rb > K > Na > Li
Explanation: Atomic radii increase as we move down Group 1 (alkali metals) due to the addition of electron shells. Thus, the correct order is Rb > K > Na > Li.
39. Which of the following alkaline earth metals has the highest second ionization energy?
- (a) Beryllium
- (b) Magnesium
- (c) Calcium
- (d) Strontium
Answer: (a) Beryllium
Explanation: Beryllium has the highest second ionization energy among the alkaline earth metals because it requires more energy to remove a second electron from the small, highly charged Be²⁺ ion.
40. Which alkali metal is used in atomic clocks?
- (a) Lithium
- (b) Sodium
- (c) Potassium
- (d) Cesium
Answer: (d) Cesium
Explanation: Cesium is used in atomic clocks because of the precise frequency of its electron transitions. Cesium atomic clocks are highly accurate for measuring time.
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