Question

Pick up the incorrect statements here. (1) Classical smog is good for health but not photochemical smog. (2) During formation of smog the level of ozone in the atmosphere goes down. (3) Classical smog has an oxidizing character while the photochemical smog is reducing in character. (4) Photochemical smog occurs in day time whereas the classical smog occurs in early morning hours. (a) 1,2 and 3 (b) 1,3 and 4 (c) 2 and 3 only (d) 3 and 4 only

Short answer

The incorrect statements are in option (a) 1, 2, and 3.

Step-by-step solution

Evaluate Statement 1

Statement 1 says that classical smog is good for health but not photochemical smog. This is incorrect because classical smog, also known as "London smog," is caused by smoke, fog, and sulfur dioxide, which are harmful to health. Photochemical smog is also harmful. Both types of smog are not good for health.

Evaluate Statement 2

Statement 2 claims that during the formation of smog, the level of ozone in the atmosphere goes down. This is incorrect in the case of photochemical smog, which actually involves the creation of ozone and other oxidizing agents. Thus, during the formation of photochemical smog, the level of ozone actually increases.

Evaluate Statement 3

Statement 3 asserts that classical smog has an oxidizing character while photochemical smog is reducing in character. This is incorrect because classical smog is reducing in nature due to its sulfurous content, while photochemical smog is oxidizing due to the presence of ozone and other oxidants.

Evaluate Statement 4

Statement 4 says photochemical smog occurs in daytime, whereas classical smog occurs in early morning hours. This is correct because photochemical smog forms in the presence of sunlight, which is available during the day, while classical smog is more common in the early morning when atmospheric conditions are cooler and more humid.

Determine the Incorrect Statements

Based on our evaluation, the incorrect statements are 1, 2, and 3. Statement 4 is correct. The choice that includes the incorrect statements 1, 2, and 3 is option (a).

Key concepts

Classical Smog

Classical smog, often referred to as "London smog," is a type of air pollution characterized by a mixture of smoke and fog. This particular smog was notorious in the early 20th century when coal burning in fireplaces was common. It occurs in cooler climates during the early morning hours when humidity is high. - The primary components of classical smog include: - Smoke, which consists of tiny particles from burning fuel, particularly coal. - Sulfur dioxide, a harmful gas released from burning fossil fuels and particularly coal combustion. Classical smog is termed as "reducing smog" because it contains chemical agents that steal oxygen while reacting with other substances. Due to these harmful compounds, it poses significant health risks, especially to those with respiratory conditions. It's especially dangerous because it can irritate the lungs and worsen pre-existing respiratory diseases.
To summarize, classical smog is unhealthy to humans and its effects were historically amplified due to industrial activities and domestic coal fires during the cold months.

Photochemical Smog

Photochemical smog, unlike classical smog, develops in the presence of sunlight. It is prevalent in urban environments with heavy vehicular traffic, as it forms when sunlight chemically reacts with human-made and natural emissions. This type of smog is especially common during warm, sunny days. - The main components involved in photochemical smog include: - Volatile Organic Compounds (VOCs) and nitrogen oxides ( NO_x ) which come from vehicle emissions, industrial processes, and some plant life. - Sunlight, which acts as a catalyst, triggering chemical reactions that form secondary pollutants such as ozone and nitric acid. Photochemical smog is often termed as "oxidizing smog" due to its composition, which includes oxidizing agents, especially ozone. Unlike classical smog, it is typically seen during daytime and can lead to eye irritation, reduced lung function, and has environmental impacts like damaging crops and reducing visibility. Addressing photochemical smog requires reducing emissions from cars and industrial sources, and adopting cleaner energy alternatives.

Ozone Formation

Ozone in the troposphere, or ground-level ozone, plays a central role in the formation of photochemical smog. It's both an important and complex topic because while ozone high up in the stratosphere (the "ozone layer") protects us from harmful ultraviolet radiation, ground-level ozone is a pollutant with significant health implications. - How Ground-Level Ozone Forms: - Ozone is not directly emitted. It forms through chemical reactions between nitrogen oxides ( NO_x ) and volatile organic compounds (VOCs) in the presence of sunlight. - The reaction typically peaks in the late afternoon as this is when solar radiation is strongest, providing abundant energy for the reactions. A key aspect of photochemical smog involves the increase in ozone levels. The increased presence of ozone acts as an indicator of photochemical activity and smog formation. Despite its harmful nature at ground level, understanding ozone formation is crucial because it helps us create strategies to improve air quality and protect public health from the potentially harmful effects associated with photochemical smog.

Reducing and Oxidizing Agents

The terms "reducing agent" and "oxidizing agent" are crucial in understanding the chemistry behind both classical and photochemical smog. These terms describe how chemicals interact with oxygen during reactions, shaping the nature of the resulting smog. - Reducing Agents: - A reducing agent is a substance that donates electrons to another substance. In doing so, it becomes oxidized itself. Classical smog, laden with sulfur dioxide, acts as a reducing environment due to these agents. - Oxidizing Agents: - An oxidizing agent, conversely, accepts electrons from another substance. In this process, it becomes reduced. Photochemical smog is rich in oxidizing agents like ozone, formed as sunlight triggers reactions between NO_x and VOCs. Understanding these agents is essential because it helps explain the fundamental differences between smog types. Classical smog’s reducing nature contrasts photochemical smog’s oxidizing nature. These distinctions are important for both chemical understanding and while assessing the specific health and environmental risks associated with each smog type. As such, our actions to mitigate these effects require tailored strategies to manage emissions and improve urban air quality.