Chemistry · Chemical bonding and molecular structure · chapter 4 of 9

Class 11 Chemistry Chapter 4: Chemical Bonding and Molecular Structure Assertion-reason questions with answers

2 assertion-reason questions on Chemical Bonding and Molecular Structure, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): In SF₄ the lone pair on sulphur occupies an equatorial position of the trigonal bipyramid. Reason (R): At an equatorial position the lone pair has only two lp–bp repulsions at 90°, while at an axial position it would have three.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

Both are true. Fewer lp–bp repulsions at 90° make the equatorial arrangement more stable, which is why the lone pair is found there: R explains A.

Question 2
Assertion (A): O₂ is paramagnetic. Reason (R): The bond order of O₂ is 2.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Both are true, but the paramagnetism comes from the two unpaired electrons in π*2px and π*2py, not from the bond order; R does not explain A.

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