The s-Block Elements

Question 213
CBSEENCH11008305

Which of the following compounds has the lowest melting point? 

  • CaBr2

  • CaI2

  • CaF2

  • CaCl2

Solution

B.

CaI2

As covalent character increases, melting point decreases, thus order of melting point is
CaF2 > CaCl2 > CaBr2 > CaI2

Question 214
CBSEENCH11008317

Which one of the following is present as an active ingredient in bleaching powder for bleaching action?

  • Ca(OCl)2

  • CaO2Cl

  • CaCl2

  • CaOCl2

Solution

D.

CaOCl2

CaOCl2, Calcium hypochlorite is the active ingredient in bleaching powder which releases chlorine.

Question 215
CBSEENCH11008321

On heating which of the following releases CO2 most easily?

  • K2CO3

  • Na2CO3

  • MgCO3

  • CaCO3

Solution

C.

MgCO3

Order of thermal stability is 
K2CO3 > Na2CO3 > CaCO3 > MgCO3
Thus, MgCO3 releases CO2 most easily
MgCO3 + heat ---> MgO + CO2

Question 216
CBSEENCH11008341

What is the value of electron gain enthalpy of Na+ if IE1 of Na = 5.1 eV?

  • -5.1 eV

  • -10.2 eV

  • +2.55 eV

  • +10.2 eV

Solution

A.

-5.1 eV

IE1 of Na = - Electron gain enthalpy of Na+ ion.
 = -5.1 eV.

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