Q62 / 200 · NEET 2007 · Chemistry

The correct order of increasing thermal stability of $\mathrm{K}_2 \mathrm{CO}_3, \mathrm{MgCO}_3, \mathrm{CaCO}_3$ and $\mathrm{BeCO}_3$ is:

  • Correct answer
    A
    $\mathrm{BeCO}_3 < \mathrm{MgCO}_3 < \mathrm{CaCO}_3 < $ $\mathrm{K}_2 \mathrm{CO}_3$
  • B
    $\mathrm{MgCO}_3 < \mathrm{BeCO}_3 < \mathrm{CaCO}_3 < \mathrm{K}_2 \mathrm{CO}_3$
  • C
    $\mathrm{K}_2 \mathrm{CO}_3 < \mathrm{MgCO}_3 < \mathrm{CaCO}_3 < $ $\mathrm{BeCO}_3$
  • D
    $\mathrm{BeCO}_3 < \mathrm{MgCO}_3 < \mathrm{K}_2 \mathrm{CO}_3 < \mathrm{CaCO}_3$

Solution

The basicity of metal hydroxides increases down the group from $\mathrm{Be}$ to $\mathrm{Ba}$, so, the thermal stability of their carbonates also increases in the same order. Also, group 1 compound are more thermally stable than group 2 because their hydroxide are much basic than group 2 hydroxides. $$ \mathrm{BeCO}_3 < \mathrm{MgCO}_3 < \mathrm{CaCO}_3 < \mathrm{K}_2 \mathrm{CO}_3 $$

Hence, the correct answer is option: 'A'.

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