Total number of CORRECT orders is:- (i) Zn + 2 A ℓ F 3 (Melting point) (iii) AgI AgCl (Colour intensity) (iv) ZnCl 2

Question

Total number of CORRECT orders is:- (i) Zn + 2 < Cd + 2 < Hg + 2 (Number of d-electrons) (ii) NaF > MgF 2 > A ℓ F 3 (Melting point) (iii) AgI > AgCl (Colour intensity) (iv) ZnCl 2 < HgCl 2 (Degree of ionisation in aqueous solution) (v) Na 2 CO 3 < MgCO 3 (Temperature required for thermal decomposition)

TestHub · Accepted Answer

(i) Correct: The total number of d-electrons increases down the group ( $Z n^{2 +}$ = 10, $C d^{2 +}$ = 20, $H g^{2 +}$ = 30).

(ii) Incorrect: Due to higher lattice energy, the correct melting point order is $N a F < M g F_{2} < A lF_{3}$ .

(iii) Correct: Due to greater polarization and covalent character (Fajans' rule), $A g I$ (dark yellow) has a higher color intensity than $A g Cl$ (white).

(iv) Incorrect: $H g Cl_{2}$ is highly covalent and barely ionizes in water, so the degree of ionization is $Z n Cl_{2} > H g Cl_{2}$ .

(v) Incorrect: Alkali metal carbonates are more thermally stable than alkaline earth metal carbonates, so $N a_{2} CO_{3} > M g CO_{3}$ .

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