## The s-Block Elements Questions and Answers Part-13

1. Which of the followng has lowest melting point?
a) $SrF_{2}$
b) $BeF_{2}$
c) $MgF_{2}$
d) $CaF_{2}$

Explanation: BeF2 being covalent has the lowest melting point (800ºC) while all other fluorides melt around 1300ºC

2. Amongst LiCl, RbCl, $BeCl_{2}$ and $MgCl_{2}$  the compounds with greatest and the least ionic character, respectively, are
a) LiCl and RbCl
b) $RbCl$  and $BeCl_{2}$
c) $RbCl$  and $MgCl_{2}$
d) $MgCl_{2}$  and $BeCl_{2}$

Explanation: $RbCl$  and $BeCl_{2}$

3. Melting point of calcium halides decreases in the order
a) $CaF_{2}>CaCl_{2}>CaBr_{2}>CaI_{2}$
b) $CaI_{2}>CaBr_{2}>CaCl_{2}>CaF_{2}$
c) $CaBr_{2}>CaI_{2}>CaF_{2}>CaCl_{2}$
d) $CaCl_{2}>CaBr_{2}>CaI_{2}>CaF_{2}$

Explanation: As the size of the anion increases, the covalent character increases and hence the mp. decrease.

4. Which liberates ammonia when treated with water?
a) $Li_{3}N$
b) $Mg_{3}N_{2}$
c) $CaCN_{2}$
d) All of these

Explanation: All nitrides react with H2O to give NH3 but CaCN2 also react with H2O to give NH3
CaNCN + 3H2O $\rightarrow$   CaCO3 + NH3

5. The value of x is maximum for
a) $MgSO_{4}.xH_{2}O$
b) $CaSO_{4}.xH_{2}O$
c) $BaSO_{4}.xH_{2}O$
d) All have the same value of x.

Explanation: Because of smaller size, Mg2+ ions are extensively hydrated.

6. Which of the following shows high tendency to form a peroxide?
a) Lithium
b) Beryllium
c) Magnesium

Explanation: Larger the size of the atom, larger is the tendency to form peroxides

7. Which of the following alkaline earth metal oxides shows a coordination number four?
a) BeO
b) MgO
c) SrO
d) CaO

Explanation: BeO

8. The basic character of the oxides $MgO , SrO ,K_{2}O,NiO ,Cs_{2}O$      increases in the order
a) $MgO > SrO >K_{2}O>NiO >Cs_{2}O$
b) $Cs_{2}O<K_{2}O<MgO< SrO<NiO$
c) $NiO < MgO < SrO<K_{2}O<Cs_{2}O$
d) $K_{2}O<NiO < MgO < SrO<Cs_{2}O$

Explanation: $NiO < MgO < SrO<K_{2}O<Cs_{2}O$

9. Which of the following has correct increasing basic strength?
a) MgO < BeO < CaO < BaO
b) BeO < MgO < CaO < BaO
c) BaO < CaO < MgO < BeO
d) CaO < BaO < BeO < MgO

c) $Al_{2}O_{3}$
d) $N_{2}O_{5}$