Environmental Chemistry (VSAQs)

Chemistry-1 | 12. Environmental Chemistry – VSAQs:
Welcome to VSAQs in Chapter 12: Environmental Chemistry. This page features the key FAQs for Very Short Answer Questions. Each answer is provided in simple English and follows the exam format. This will assist in focusing on important details and achieving top marks in your final exams.

VSAQ-1 : What is chemical Oxygen Demand (COD)?

Chemical Oxygen Demand (COD) is a measure of the “amount of oxygen needed” to chemically oxidize the organic and inorganic substances present in polluted water. It is utilized as an indicator to assess the “level of water pollution,” particularly in industrial and wastewater treatment contexts.

VSAQ-2 : What is Biochemical oxygen demand (BOD)?

Biochemical Oxygen Demand (BOD) is the “amount of oxygen consumed” by microorganisms in water over a period of five days at 20°C. BOD is employed as an indicator to assess the “level of water pollution,” particularly in evaluating the impact of organic contaminants on aquatic ecosystems.

VSAQ-3 : Which oxides cause acid rain? And what is its pH value?

The oxides that cause acid rain are primarily oxides of nitrogen (NOx), sulfur dioxide (SO2), and to a lesser extent, carbon dioxide (CO2) when it dissolves in rainwater.

The pH of acid rain typically ranges from 4.2 to 5.6, with an average pH of about 5.6.

VSAQ-4 : Acid rains are harmful. Why? (or) Name two adverse effects caused by acid rains.

Acid rain is harmful because it

  1. Damages Structures: Acid rain can corrode and erode buildings, historical monuments, and infrastructure, leading to their deterioration and reduced lifespan.
  2. Affects Soil Fertility: It decreases soil pH, leading to soil acidification, which can harm plant growth and reduce soil fertility.

These adverse effects can have wide-ranging environmental, economic, and health impacts, affecting both natural and man-made environments.

VSAQ-5 : What happens when holes are formed in ozone layer? Mention the harmful effects due to depletion of ozone layer.

When holes form in the ozone layer, harmful ultraviolet (UV) rays from the sun penetrate these openings and reach the Earth’s surface. Depletion of the ozone layer has various harmful effects:

  1. Skin Cancer: Increased UV ray exposure can elevate the incidence of skin cancer in humans.
  2. Cataracts: UV radiation contributes to the development of cataracts in the eyes.
  3. Environmental Impact: Ozone depletion disrupts ecosystems, diminishes soil moisture, and decreases agricultural productivity. It also harms phytoplankton in oceans, disrupting the marine food chain.
  4. Impact on Photosynthesis: Elevated UV levels negatively affect photosynthesis in plants, leading to reduced crop yields and stunted plant growth.

VSAQ-6 : Define Green house effect. Which gases are the cause for it?

The greenhouse effect refers to the gradual warming of the Earth’s surface, primarily caused by the “blanketing effect” of specific gases in the atmosphere. These gases, collectively known as greenhouse gases, encompass:

  1. Carbon dioxide (CO2)
  2. Methane (CH4)
  3. Ozone (O3)
  4. Chlorofluorocarbons (CFCs)
  5. Water vapor

VSAQ-7 : What happens when carbon monoxide is increased in air?

Increased Carbon Monoxide (CO) in Air

When the concentration of carbon monoxide (CO) in the air rises, it can have detrimental effects on human health:

  1. Formation of Carboxyhemoglobin: Inhaling CO leads to its binding with hemoglobin in the bloodstream, forming a stable complex known as carboxyhemoglobin. This reduces hemoglobin’s ability to carry oxygen, resulting in oxygen deprivation in body tissues.
  2. Health Effects: Elevated CO levels in the air can induce symptoms such as dizziness, headaches, nausea, confusion, and shortness of breath. In severe cases, it can progress to loss of consciousness (coma) and, in extreme instances, death due to oxygen deprivation.

It is crucial to prevent exposure to high levels of carbon monoxide and ensure proper ventilation and safety measures in areas where CO may be generated, such as homes with gas appliances or enclosed spaces with running vehicles.

VSAQ-8 : Define Receptor, sink and speciation.

  1. Receptor: The receptor refers to the medium or environment that is adversely affected by pollutants. It can encompass various elements such as air, water, soil, or any other system that experiences the presence and impact of pollutants.
  2. Sink: A sink denotes a medium or location within the environment that retains and interacts with pollutants, thereby reducing their concentration and mitigating their effects. Sinks can take the form of natural systems like forests, bodies of water, or even specific materials used for pollution control.
  3. Speciation: Speciation involves the examination of the various chemical forms or compounds in which pollutants exist within the environment. Understanding speciation is crucial because different forms of pollutants can exhibit varying toxicities and behaviors, ultimately influencing their impact on ecosystems and human health.

VSAQ-9 : Name two important sinks for Carbon dioxide.

Two Important Sinks for Carbon Dioxide (CO2):

  1. Ocean Water: The Earth’s oceans serve as a pivotal sink for carbon dioxide (CO2) by absorbing a substantial portion of atmospheric CO2. This oceanic absorption process plays a crucial role in regulating CO2 levels in the atmosphere.
  2. Forests and Vegetation: Forests and other forms of vegetation are essential in carbon sequestration. Through photosynthesis, they actively capture CO2 from the air and store carbon within their biomass and the soil. As a result, forests and vegetation serve as significant carbon sinks in terrestrial ecosystems.

VSAQ-10 : What are smoke and mist?

  1. Smoke: Smoke is a combination of carbon dioxide (CO2), water vapor, and minuscule soot particles produced during the combustion and burning of organic substances.
  2. Mist: Mist, in contrast, is composed of minuscule liquid droplets formed when water vapor condenses in the atmosphere. Mist typically presents itself as a collection of fine droplets, creating a hazy or foggy appearance in the air.

VSAQ-11 : What is PAN? What effect is caused by it?

PAN (Peroxyacetyl Nitrate): PAN, also known as peroxyacetyl nitrate (C₂H₃O₅N), is a constituent of photochemical smog and is associated with several detrimental effects:

Effects Caused by PAN:

  1. Toxicity: PAN possesses toxic properties and can be harmful to human health upon exposure.
  2. Respiratory and Eye Irritation: Inhalation of PAN can result in respiratory irritation and eye irritation, leading to discomfort and potential health issues.
  3. Corrosion: PAN is capable of corroding metals, building materials, rubber, and painted surfaces, leading to damage to infrastructure and materials.

Reducing the presence of PAN and other pollutants in the atmosphere is crucial to mitigate these adverse effects on both human health and the environment.

VSAQ-12 : Name the common components of Photochemical smog.

Common Components of Photochemical Smog:

Photochemical smog typically comprises the following common components:

  1. Ozone (O3)
  2. Nitric Oxide (NO)
  3. Formaldehyde (CH2O)
  4. Acrolein
  5. Peroxyacetyl Nitrate (PAN)

These pollutants have the ability to interact in the presence of sunlight, leading to the formation of smog, which can negatively impact air quality and human health.

VSAQ-13 : Define Pollutant and Contaminant.

  1. Pollutant: A pollutant is an undesired waste material that is usually harmful to both humans and the environment. Pollutants are often found in larger quantities in the environment than their natural occurrence would suggest. Examples of pollutants encompass carbon monoxide (CO), sulfur dioxide (SO2), ozone (O3), plastic materials, and pesticides like DDT.
  2. Contaminant: A contaminant is an undesired waste material that is generally less harmful to humans compared to pollutants. Contaminants are substances introduced into the environment through human activities and are not typically present in nature. Examples of contaminants include industrial effluents, pesticides, and hazardous gases like methyl isocyanate (MIC).

VSAQ-14 : What is harm caused by CFCs?

Harm Caused by CFCs (Chlorofluorocarbons)

CFCs are harmful primarily due to their role in contributing to the depletion of the ozone layer in the Earth’s atmosphere. This ozone layer depletion has several adverse consequences:

  1. Increased UV Radiation: Ozone layer depletion allows harmful ultraviolet (UV) radiation from the sun to penetrate the atmosphere and reach the Earth’s surface. This heightened UV exposure poses health risks, including an elevated risk of skin cancer and cataracts in humans.
  2. Environmental Disruption: Ozone depletion has environmental impacts, leading to disruptions in ecosystems and various other detrimental effects on the environment and wildlife.

VSAQ-15 : What happens when Fluorides are present in water?

Effects of Fluorides in Water

The presence of excess fluorides in water can result in a condition known as “fluorosis,” characterized by the following effects:

  1. Discoloration of Teeth: Fluorosis can lead to the development of yellow or brown stains on teeth and may cause pitting or mottling of the tooth enamel.
  2. Weakening of Bones: Elevated levels of fluorides in water can weaken bones, making them more prone to fractures.

It’s essential to emphasize that the concentration of fluorides in drinking water should not exceed 3 parts per million (ppm) to prevent health issues. The interaction of fluorides with calcium in bones and teeth forms calcium fluoride (CaF2), contributing to these adverse effects.

VSAQ-16 : Explain the strategies adopted in Green chemistry to avoid environmental pollution.

Strategies in Green Chemistry to Prevent Environmental Pollution

Green chemistry embraces several strategies to promote eco-friendly practices and minimize environmental pollution:

  1. Cost-Effective Approach: Prioritizing cost efficiency in processes and products encourages the development of sustainable alternatives that are economically viable.
  2. Reduced Chemical Use: Green chemistry emphasizes the minimization of chemical usage, leading to a reduction in the generation of hazardous waste and the potential for environmental contamination.
  3. Energy Efficiency: The approach focuses on minimizing energy consumption, reducing greenhouse gas emissions, and conserving natural resources during chemical processes.
  4. Waste Minimization: Green chemistry aims to minimize waste generation through the design of more efficient processes and the use of renewable feedstocks, thereby decreasing the environmental impact of chemical production.