p-Block Elements

A

colourless gas + residue Residue + H 2 O $\to$ B

C

A This is possible only when ‘A’ is CaCO 3 . The reactions are as follow :

The hydration enthalpy of BeSO 4 is higher than its lattice energy.

Within group 2, the hydration energy decreases down the group while lattice energy is almost the same.

On moving down the group, basic nature of these hydroxides increases due to low ionization enthalpies because M-O bond in MOH is weak and thus break to give OH – ions in the solution.

NaOH is a strong alkali.

It combines with acidic and amphoteric oxides to form salts.

Since CaO is a basic oxide hence does not reacts with NaOH.

According to Fajans’ rule, Covalent character $\propto$ size of anion $\propto$ 1 size of cation .

Now the order of size of anions in the given options is as follows F – < Cl – < Br – < I – Thus, the covalent character of the given compounds varies as MI > MBr > MCl > MF

Equimolar solutions of the given chlorides when prepared in water forms their respective hydroxides.

SrCl 2 + 2H 2 O $\to$ Sr(OH) 2 + 2HCl BaCl 2 + 2H 2 O $\to$ Ba(OH) 2 + 2HCl MgCl 2 + 2H 2 O $\to$ Mg(OH) 2 + 2HCl CaCl 2 + 2H 2 O $\to$ Ca(OH) 2 + 2HCl Be(OH) 2 is amphoteric, but the hydroxides of other alkaline earth metals are basic.

The basic strength increases down the group.

Hence higher the basic character higher will be the pH.

Smaller the size of an ion, greater will be the degree of hydration.

So, degree of hydration is highest for Li + and that is smallest for Cs + .

Therefore, Li + holds the water molecules in its hydration sphere and Cs + ion holds the least water molecules.

Hence, the correct ionic mobility in aqueous medium is : Cs + > Rb + > K + > Na +

The stability of alkali metal hydrides decreases from Li to Cs.

It is due to the fact that M–H bonds becomes weaker with increase in size of alkali metals as we move down the group from Li to Cs.

Thus the order of stability of hydrides is LiH > NaH > KH > RbH > CsH

As the basicity of metal hydroxides increases down the group from Be to Ba, the thermal stability of their carbonates also increases in the same order.

Further group 1 compounds are more thermally stable than group 2 because their hydroxide are much basic than group 2 hydroxides therefore, the order of thermal stability is BeCO 3 < MgCO 3 < CaCO 3 < K 2 CO 3

Hydration energy of sulphate decreases on moving down the group-II.

Mg 2+ is smaller than other ions of group II, so Mg 2+ is readily hydrated and hence MgSO 4 has higher hydration energy than the lattice energy.