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s-Block Elements · Question 34

AIPMT 2008MCQEasy📈 Topic in 25% papers+4−1
1

The alkali metals form salt-like hydrides by the direct synthesis at elevated temperature. The thermal stability of these hydrides decreases in which of the following orders?

  1. NaH > LiH > KH > RbH > CsH
  2. LiH > NaH > KH > RbH > CsH
  3. CsH > RbH > KH > NaH > LiH
  4. KH > NaH > LiH > CsH > RbH

Answer

(2) LiH > NaH > KH > RbH > CsH

Solution

As per NCERT, alkali metals react with dihydrogen at about 673 K to form ionic hydrides M+H-.

∵ Down the group the size of M+ increases, so the lattice enthalpy of M+H- decreases.

⇒ The smallest cation Li+ gives the most stable hydride; LiH is the most stable alkali metal hydride.

∴ Thermal stability decreases as LiH > NaH > KH > RbH > CsH

Answer: (2)

Out of syllabusAIPMT 2008

Keep practising — s-Block Elements

2

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
Out of syllabusAIPMT 2007
3

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
4

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
5

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
6

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
7

Mg is present in

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

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