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s-Block Elements · Question 35

AIPMT 2007MCQEasy📈 Topic in 12% papers+4−1
1

The correct order of increasing thermal stability of K2CO3, MgCO3, CaCO3 and BeCO3 is

  1. BeCO3 < MgCO3 < CaCO3 < K2CO3
  2. MgCO3 < BeCO3 < CaCO3 < K2CO3
  3. K2CO3 < MgCO3 < CaCO3 < BeCO3
  4. BeCO3 < MgCO3 < K2CO3 < CaCO3

Answer

(1) BeCO3 < MgCO3 < CaCO3 < K2CO3

Solution

As per NCERT, the carbonates of alkaline earth metals decompose on heating, and their thermal stability increases down the group with increasing cationic size: MCO3 MO + CO2

∵ Be2+ is the smallest cation, it polarises CO32- the most ⇒ BeCO3 is the least stable.

⇒ BeCO3 < MgCO3 < CaCO3

⇒ K+ is large and singly charged (very low polarising power), so K2CO3 does not decompose even at high temperature; alkali metal carbonates are more stable than alkaline earth metal carbonates.

∴ BeCO3 < MgCO3 < CaCO3 < K2CO3

Answer: (1)

Out of syllabusAIPMT 2007

Keep practising — s-Block Elements

2

In which of the following the hydration energy is higher than the lattice energy?

  1. MgSO4
  2. RaSO4
  3. SrSO4
  4. BaSO4
Out of syllabusAIPMT 2007
3

The correct order of the mobility of the alkali metal ions in aqueous solution is

  1. Rb+ > K+ > Na+ > Li+
  2. Li+ > Na+ > K+ > Rb+
  3. Na+ > K+ > Rb+ > Li+
  4. K+ > Rb+ > Na+ > Li+
Out of syllabusAIPMT 2006
4

A solid compound X on heating gives CO2 gas and a residue. The residue mixed with water forms Y. On passing an excess of CO2 through Y in water, a clear solution Z is obtained. On boiling Z, compound X is reformed. The compound X is

  1. Ca(HCO3)2
  2. CaCO3
  3. Na2CO3
  4. K2CO3
Out of syllabusAIPMT 2004
5

In which of the following processes, fused sodium hydroxide is electrolysed at a temperature of 330 C for extraction of sodium?

  1. Castner's process
  2. Downs process
  3. Cyanide process
  4. Both (2) and (3)
Out of syllabusAIPMT 2002
6

Mg is present in

  1. chlorophyll
  2. haemoglobin
  3. vitamin-D
  4. vitamin-B
AIPMT 2000

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