Which one of the following metals produces dinitrogen oxide with dilute nitric acid and nitrogen dioxide with concentrated nitric acid?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Zinc
The product of a metal with nitric acid depends on the concentration of the acid and on the nature of the metal. Concentrated nitric acid generally gives NO2. With dilute acid, a less active metal such as copper gives NO, while a more active metal such as zinc reduces the nitrate further, to N2O:
\( \displaystyle \ce{4Zn + 10HNO3 (dilute) -> 4Zn(NO3)2 + 5H2O + N2O} \)
\( \displaystyle \ce{Zn + 4HNO3 (conc.) -> Zn(NO3)2 + 2H2O + 2NO2} \)
Copper, a less active metal, gives NO with dilute nitric acid instead of \( \ce{N2O} \):
\( \ce{3Cu + 8HNO3 (dilute) -> 3Cu(NO3)2 + 2NO + 4H2O} \)
Note: 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):
Nitric Acid – …
