JEE Main 2023 · 29 January · evening · Numerical answer · +4 / −0
Total number of acidic oxides among
N₂O₃,NO₂,N₂O,Cl₂O₇,SO₂,CO,CaO,Na₂O and NO is ____________.
Answer and solution
Answer 4
Solution
Chemistry ma’am · 3 steps
Not every non-metal oxide is acidic: first set aside the neutral ones, CO, NO and N₂O.
- Sort by element. Oxides of active metals like Na and Ca are basic. Most non-metal oxides are acidic, because they react with water to give an acid.
- Neutral exceptions. Three non-metal oxides give no acid with water and do not react with acids or bases: CO, NO and N₂O. They are neutral, so they do not count.
Type Oxides Reason Acidic N₂O₃, NO₂, Cl₂O₇, SO₂ give HNO₂, HNO₃ + HNO₂, HClO₄, H₂SO₃ with water Neutral N₂O, NO, CO no acid formed, no salt with acids or bases Basic CaO, Na₂O give Ca(OH)₂ and NaOH with water - So. The acidic oxides are N₂O₃, NO₂, Cl₂O₇ and SO₂, so the count is 4.
The common slip: 7. Counting CO, NO and N₂O as acidic just because they are non-metal oxides gives 7. These three are neutral.
The idea to keep. Learn the neutral oxides by heart: CO, NO, N₂O (and H₂O). Apart from these, a non-metal oxide is acidic, and an active metal oxide is basic.
Answer from the NTA final answer key. Solution by PrepWiser.