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The s-block Elements — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe s-block Elements3 Marks
Question
Give reasons:
  1. Beryllium halides are polymeric.
  2. $Be(OH)_2$ dissolves in NaOH but $Mg(OH)_2$ does not.
  3. MgO is used as refractory material.
✓

Answer

  1. $BeCl_2$ is lewis acid, electron deficient, therefore, forms polymeric structure.
  2. $Be(OH)_2$​​​​​​​ is amphoteric therefore, dissolves in NaOH but $Mg(OH)_2​​​​​​​$​​​​​​​ is basic does not react with NaOH.
$\text{Be(OH)}_2+2\text{NaOH}\xrightarrow{\ \ \ \ \ \ \ \ }\text{Na}_2[\text{Be(OH)}_4]\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{(Soluble)}$
  1. MgO has high melting point due to high lattice energy, therefore, used as refractory material.

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