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Chemical Bonding and Molecular Structure — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryChemical Bonding and Molecular Structure1 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 each question.
Assertion $(A)$ : Though the central atom of both $\mathrm{NH}_3$ and $\mathrm{H}_2 \mathrm{O}$ molecules are $\mathrm{sp}^3$ hybridised, yet $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle is greater than that of $\mathrm{H}-\mathrm{O}-\mathrm{H}$.
Reason $(R)$ : This is because nitrogen atom has one lone pair and oxygen atom has two lone pairs.
  • ✓
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • B
    $A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
  • C
    $A$ is true but $R$ is false.
  • D
    $A$ and $R$ both are false.
✓

Answer

Correct option: A.
$A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
$\mathrm{H}_2 \mathrm{O}$ has two lone pairs while $\mathrm{NH}_3$ has single lone pair, hence, $\mathrm{H}_2 \mathrm{O}$ involves greater lone pair-bond pair repulsion.

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