Answer the question on the basis of the passage given below:
Oxides formed by \(p\)- block elements are acidic, basic and neutral. Also, elements of \(p\)-block form different acids.
For the following oxides, which of the following will be true?
\(SO_3, CO_2, SiO_2, N_2O_5\)
A. \(CO_2\) is an acidic oxide.
B. \(CO_2\) is a neutral oxide.
C. \(SO_3 > N_2O_5 > CO_2 ≈ SiO_2\) decreasing order of central atom oxidation states
D. \(SO_3 < N_2O_5 < CO_2 ≈ SiO_2 \rightarrow\) increasing order of central atom oxidation states
Choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A and C only
Note 1: None of the given options was correct in the NTA question paper. To provide additional question practice to the students, the question has been slightly modified so that the question has one clear answer.
Oxides of non-metals are generally acidic: they give acids with water. The oxidation state of the central atom in each oxide is found from the charge balance (O = −2):
\( \ce{SO3} \): S = +6 \( \ce{N2O5} \): N = +5 \( \ce{CO2} \): C = +4 \( \ce{SiO2} \): Si = +4
(A) \( \ce{CO2} \) is an acidic oxide. — Correct. It dissolves in water to give carbonic acid.
\( \ce{CO2 + H2O <=> H2CO3} \)
(B) \( \ce{CO2} \) is a neutral oxide. — Incorrect. The neutral oxides of carbon and nitrogen are CO, NO and \( \ce{N2O} \), not \( \ce{CO2} \).
(C) \( \ce{SO3} \) > \( \ce{N2O5} \) > \( \ce{CO2} \) ≈ \( \ce{SiO2} \) decreasing order of central atom oxidation states — Correct. +6 > +5 > +4 = +4.
(D) \( \ce{SO3} \) < \( \ce{N2O5} \) < \( \ce{CO2} \) ≈ \( \ce{SiO2} \) → increasing order of central atom oxidation states — Incorrect. It would need +6 < +5 < +4, which is false; the oxidation states fall from \( \ce{SO3} \) to \( \ce{CO2} \).
Note 2: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Simple Oxides – …
