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

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe s-block Elements1 Mark
MCQ
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below question.
Assertion $(A)$ : The carbonate of lithium decomposes easily on heating to form lithium oxide and $\mathrm{CO}_2$.
Reason $(R)$ : Lithium being very small in size polarises large carbonate ion leading to the formation of more stable $\mathrm{Li}_2 \mathrm{O}$ and $\mathrm{CO}_2$.
  • ✓
    Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
  • B
    Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A.$
  • C
    Both $A$ and $R$ are not correct.
  • D
    $A$ is not correct but $R$ is correct.
✓

Answer

Correct option: A.
Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
$\mathrm{Li}_2 \mathrm{CO}_3$ is unstable and decomposes on heating. Due to small size of $\mathrm{Li}^{+}$. It has strong polarizing power to disort electron cloud of $\mathrm{CO}_3^{-2}$. Lattice energy of $\mathrm{Li}_2 \mathrm{O}$ is higher than $\mathrm{Li}_2 \mathrm{CO}_3$.

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