Assertion & Reason Test: The s-Block Elements (Old NCERT) - NEET MCQ

(i) Li - Due to very high hydration enthalpy, E⁰ is most negative.

(ii) Na - Na gives NaOH (strong base). One mole of it replaces 1 mol H⁺ from acid therefore it is the strongest monoacidic base.

(iii) Ca - Hydration energy is very low therefore, calcium oxalate is insoluble.

(iv) Ba - Hydration energy is low as the size Ba²⁺ is large therefore barium sulphate is insoluble. 6s² is valence shell electronic configuration.

(i) CaCO₃ - Specially precipitated CaCO₃ ​is used in the manufacture of high quality paper.

(ii) Ca(OH)₂ - It is used in white wash due to its disinfectant nature and sparingly soluble in water.

(iii) CaO - It is used in the manufacture of Na₂CO₃ ​ from NaOH.

(iv) CaSO₄ - It is used in dentistry and ornamental work.

Correct option is A.  A. →(6) B. →(4) C. →(3) E. →(5). F. →(1)
Elements with the characteristic flame colour are as follows
A. Cs-Blue B. Na-Yellow C. K-Violet
D. Ca-Brick red E. Sr-Crimson red F. Ba-Apple green
Flame colours are produced from the movement of the electron in the metal ions present in the compounds. These movement of electrons (electronic excitation-de-excitation) requires energy. Each atom has particular energy gap between ground and excited energy level therefore each of these movement involves a specific amount of energy emitted as light energy, and each corresponds to a particular colour. As we know energy gap between ground and excited state energy level increases wavelength of decreases and complemently coloure is observed as a result.

Li₂CO₃ → Li₂O + CO₂

Polarisation is the distortion of electron cloud of the anion CO₃^2- by the cation Li²⁺.

BeCO₃ ​⇌ BeO + CO₂ ​

When they are stored in the atmosphere of CO₂, the concentration of CO₂ increases in the right side, making the reaction to shift towards backside so that the decomposition of beryllium carbonate is prevented.

• Beryllium does not exhibit coordination number more than four as in its valence shell there are only four orbitals.

• Beryllium oxide is amphoteric in nature.

Although Li exhibits, the characteristic properties of alkali metals it differs at the same time in many of its properties from alkali metals.
The anomalous behaviour of lithium is due to the extremely small size of lithium and its cation. On account of the small size and high nuclear charge, lithium exerts the greatest polarising effect out of all alkali metals on negative ions.

Answers:

(a) Exceptionally small size of its atom
(b) Its high polarising power

CaCl₂ ​+ 2Na⁺ → Ca(Al−silicate)₂ ​+ 2NaCl

MgCl₂ ​ + 2Na⁺ → Ca(Al−silicate)₂ ​+ 2MgCl

So here the sodium ions are exchanged with both Ca²⁺ and Mg²⁺ ions.