The S-block Elements

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Correct option (ii)

On adding water to cement it gets harder over a period of time. This is known as setting of cement. Gypsum is added to the cement to slow the setting time of cement which occurs in the presence of water.

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Correct option (i)

The alkali metals dissolve in liquid ammonia and give a blue solution, which is conductive in nature. A solution of sodium in liquid ammonia at −30^? C conducts electricity. The ammoniated electrons are responsible for the blue color of the solution as they absorb energy in the visible region of light and impart blue color to the solution.

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Correct option (i)

Sodium carbonate is prepared by Solvay's process. In this process, ammonia is recovered when ammonium chloride reacts with calcium hydroxide. On reacting NH₄Cl with Ca (OH)₂ calcium chloride is obtained as a by-product. The reaction is given below.

2NH₄Cl+Ca (OH)₂→2NH₃+CaCl₂+H₂O

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Correct option (i)

Be (OH)₂ is amphoteric. It reacts with both acids and bases. It reacts with acid to form beryllium chloride and it reacts with base to form beryllate ion which is soluble in sodium hydroxide. The reaction is shown below.

Be (OH)₂+2OH⁻→ [Be (OH)₄]²⁻

Be (OH)₂+2HCl→BeCl₂+2H₂O

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Correct option (ii)

The solubility of salt depends on the lattice and hydration energy both. By increasing lattice energy and decreasing hydration energy solubility decreases. In case of biE, both the ions are small, thus the compound has high lattice energy and is insoluble in water. If both the cations and anions are comparable in size, then stability is maximum and solubility is minimum

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Correct Option (iii)On moving down the group as the size increases, the nuclear charge attraction decreases. The effect of increasing size outweighs the increasing nuclear charge. Thus, ionization enthalpy decreases. The order of decreasing ionization enthalpy is,

Li>Na>K>Rb

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Correct option (i)

BeCl₂ is covalent in nature due to the high polarising power of beryllium (+2) ion. On moving down the group, as the size increases, covalent nature decreases. Therefore, beryllium chloride being most covalent is soluble in ethanol.

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Correct option (i)

As the size of the metal increases, the basic character of the hydroxide increases down the group. The solubility of hydroxide increases, and hydroxide of Be and Mg is almost insoluble.

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Correct option (i)

Due to the smaller size of the cation Be²⁺, and larger size of the anion CO₃^2? , BeCO₃ is unstable in air. Therefore, it is kept in CO₂ atmosphere to avoid decomposition.

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Correct option (iv)

BaCO₃ will be the most thermal stable. The size of Ba²⁺ is very large due to which it has low Polarising power and cannot polarise the oxygen atom. As the positive ions gets larger on moving down the group, the effect on the carbonate ion near them decreases. Thus, the carbonate ions of large cations are stable.