• # question_answer Which of the following order are correct? (i) Solubility in water$LiOH<NaOH<KOH<RbOH<CsOH$ (ii) Thermal stability$BeS{{O}_{4}}<MgS{{O}_{4}}<CaS{{O}_{4}}<SrS{{O}_{4}}<BaS{{O}_{4}}$ (iii) Melting point $NaCl>KCl>RbCl>CsCl>LiCl$ (iv) Solubility in water $L{{i}_{2}}C{{O}_{3}}<N{{a}_{2}}C{{O}_{3}}<{{K}_{2}}C{{O}_{3}}<R{{b}_{2}}C{{O}_{3}}$ A)  I, II and III                   B)  I, II and IV       C)  II, III and IV                 D)  All of these

 (i) Solubility of hydroxides of alkali metals increases with increase in the size of alkali metal ion. (ii) Thermal stability of alkaline earth metal sulphate increases on moving downwards due to their similar lattice energy and decrease in hydration energy. (iii) Melting point $=5\times {{10}^{-3}}\times 100=0.5\,\,V$ ionic character. (iv) Solubility of carbonates of alkali metal increases on moving downwards.