Question

Which of the following were constituents of the famous classical London smog?
A. Smoke
B. Fog
C. SO\(_2\)
D. Peroxyacetyl nitrate
E. Ozone

• A. A, B and E only
• B. A, B and C only
• C. A, B, C and D only
• D. A, B, C and E only

Hint:

- London Smog (Classical): Cool, damp, sulfurous. Key ingredients: Smoke, Fog, SO\(_2\). - L.A. Smog (Photochemical): Hot, sunny, oxidizing. Key ingredients: NOx, VOCs, Sunlight, Ozone, PAN.

Answer 1

The Correct Option is B

Step 1: Define classical (London) smog.
Classical smog, also called sulfurous or industrial smog, arises mainly from burning high-sulfur coal in industrial and residential areas. It typically appears during cold, humid, and still weather.

Step 2: Identify key components. - The word "smog" combines "smoke" (particulates/soot from burning coal) and "fog" (water vapor). Therefore, A and B are essential. - High sulfur coal releases significant sulfur dioxide (SO\(_2\)), a primary pollutant in this smog. SO\(_2\) can react with water to create sulfuric acid, a key cause of acid rain. Hence, C is essential.

Step 3: Distinguish from photochemical smog. - Peroxyacetyl nitrate (PAN) (D) and Ozone (E) are characteristic of photochemical smog (Los Angeles-type). This smog forms when sunlight reacts with nitrogen oxides and volatile organic compounds from vehicle emissions. It is oxidizing, unlike London smog which is reducing.

Conclusion: London smog's constituents are Smoke (A), Fog (B), and SO\(_2\) (C).