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 known as sulfurous smog or industrial smog, is formed primarily from the burning of large amounts of high-sulfur coal in industrial and residential areas. It typically occurs under cold, humid, and calm weather conditions.

Step 2: Identify the key ingredients. - The term "smog" is a portmanteau of smoke (particulates/soot from burning coal) and fog (water vapor). So, A and B are core components. - The high sulfur content in the coal releases large amounts of sulfur dioxide (SO\(_2\)), which is a primary pollutant in this type of smog. SO\(_2\) can further react with water to form sulfuric acid, a major cause of acid rain. So, C is a core component.

Step 3: Differentiate from photochemical smog. - Peroxyacetyl nitrate (PAN) (D) and Ozone (E) are characteristic components of photochemical smog (or Los Angeles-type smog). This type of smog is formed when sunlight reacts with nitrogen oxides and volatile organic compounds from vehicle exhaust. It is oxidizing in nature, whereas London smog is reducing. Conclusion: The constituents of classical London smog are Smoke (A), Fog (B), and SO\(_2\) (C).