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) \[CaF_{2}\]

Answer: b
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 \[BeCl_{2}\]

Answer: b
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) \[CaCl_{2}>CaBr_{2}>CaI_{2}>CaF_{2}\]

Answer: a
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

Answer: d
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.

Answer: a
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
d) Radium

Answer: d
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

Answer: a
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) \[K_{2}O<NiO < MgO < SrO<Cs_{2}O\]

Answer: c
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

Answer: b
Explanation: The basic character of oxides increases down the group

10. Among the following oxides, the one which is most basic is
a) ZnO
b) MgO
c) \[Al_{2}O_{3}\]
d) \[N_{2}O_{5}\]

Answer: b
Explanation: N2O5 is strongly acidic, ZnO and Al2O3 are amphoteric, therefore, MgO is most basic