Question

Identify the gas that is responsible for the brown color of photochemical smog.

Short answer

Nitrogen dioxide (NO2) is responsible for the brown color of photochemical smog.

Step-by-step solution

Understand Photochemical Smog

Photochemical smog is a type of air pollution that results from the reaction of sunlight with pollutants such as nitrogen oxides and volatile organic compounds (VOCs) in the atmosphere. It is commonly seen in urban areas and is known for its harmful health effects and characteristic brownish color.

Identify the Key Pollutants in Photochemical Smog

The key pollutants that contribute to the formation of photochemical smog are nitrogen oxides (NOx) and volatile organic compounds (VOCs). Among these, nitrogen dioxide (NO2) is particularly significant because it gives smog its brown coloration.

Determine Which Gas Causes the Brown Color

To determine the responsible gas for the brown color in photochemical smog, focus on nitrogen oxides, specifically nitrogen dioxide (NO2). NO2 is a reddish-brown gas, and its presence in the atmosphere causes the characteristic brown haze of smog.

Key concepts

Nitrogen Oxides

Nitrogen oxides, commonly referred to as NOx, are a group of gases composed of nitrogen and oxygen. These gases are key contributors to air pollution and play a crucial role in the formation of photochemical smog.

• NOx is primarily composed of nitric oxide (NO) and nitrogen dioxide (NO2).
• They are produced from high-temperature combustion processes, such as those in car engines and power plants.

These gases contribute to a variety of environmental problems, including acid rain and the formation of ground-level ozone.
Nitrogen oxides are particularly harmful to human health, as they can cause respiratory issues and exacerbate conditions like asthma. Reducing emissions from vehicles and industrial sources is essential to mitigate the impacts of NOx on air quality.

Volatile Organic Compounds

Volatile Organic Compounds, or VOCs, are another essential component in the formation of photochemical smog. These are organic chemicals that have a high vapor pressure at room temperature.

• VOCs are emitted from products such as paints, varnishes, and vehicle exhaust.
• These compounds are highly reactive and can combine with nitrogen oxides under sunlight to form smog.

VOCs are not only contributors to air pollution but can also be harmful to health, causing issues like headaches, dizziness, and even more serious health problems with prolonged exposure. Controlling VOC emissions is crucial for improving air quality in urban environments.

Nitrogen Dioxide

Nitrogen Dioxide, symbolized as NO2, is a reddish-brown gas that is an important component of nitrogen oxides. It is particularly notable in the context of photochemical smog because it is responsible for the smog's characteristic brownish color.

• NO2 is formed when nitric oxide (NO) reacts with oxygen in the atmosphere.
• This gas is highly reactive and is a strong oxidizing agent.

The presence of NO2 in the air can lead to serious health effects, including respiratory problems and the aggravation of heart diseases. It also plays a role in the formation of ground-level ozone, further exacerbating the impact of urban air pollution.

Air Pollution

Air pollution is a major environmental issue characterized by the presence of harmful or excessive quantities of substances in the atmosphere. It can have severe effects on human health, ecosystems, and the climate.

• The chief contributors to air pollution include emissions from vehicles, industries, and natural sources such as wildfires and volcanic activities.
• Air pollution can manifest in various forms, including gases like nitrogen oxides, particulate matter, and smog.

Managing air quality and mitigating pollution is critical for safeguarding public health and the environment. Various regulations and technologies are implemented worldwide to reduce emissions and monitor air quality.

Urban Pollution

Urban pollution refers to the contamination of the urban environment due to human activities. It is a significant concern as cities expand and industrialize.

• High population density in cities leads to increased pollution from vehicles, industrial activities, and energy production.
• Photochemical smog is a common problem in urban areas, resulting from the interaction of sunlight with pollutants like NOx and VOCs.

The effects of urban pollution are widespread, affecting air quality, visibility, and public health. Cities are implementing various measures such as encouraging public transportation, enhancing green spaces, and adopting cleaner technologies to combat urban pollution and improve living conditions.