Looking for comprehensive solutions to the exercise questions of Chapter 14 Environmental Chemistry – Water for the Federal Board? This webpage provides detailed answers to all the exercise questions, including multiple-choice questions (MCQs), short-answer questions, and long-answer questions. Tailored specifically for college students under the Federal Board of Islamabad, our solutions cover key topics such as the distribution of water, water treatment methods, pollution impacts, and measures for water conservation.
Choose the Correct Answer
(ii) How much of the total water of the planet is present in the oceans?
Answer: (a) 90%
Explanation: About 90% of the Earth’s water is stored in oceans, making them the largest reservoir of water on the planet.
(iii) What type of pollutants can cause eutrophication?
Answer: (a) Agricultural
Explanation: Eutrophication is caused by agricultural pollutants, especially fertilizers rich in nitrates and phosphates, which promote excessive growth of algae in water bodies.
(iv) In which method are the small particles coagulated into big particles and then separated?
Answer: (b) Coagulation
Explanation: Coagulation involves adding substances like alum to water, causing small suspended particles to combine into larger clumps that can be easily removed by sedimentation or filtration.
(v) Which pollution can cause cancer?
Answer: (d) Heavy metals
Explanation: Pollutants like heavy metals (e.g., lead, mercury, cadmium) are toxic and carcinogenic, meaning they can cause cancer when ingested or absorbed by living organisms.
(vi) Disinfection of water is done by:
Answer: (d) All of the above
Explanation: Disinfection methods such as ozonation, UV radiation, and chlorination are widely used to kill microorganisms and make water safe for consumption.
(vii) World sources of freshwater are _ day by day.
Answer: (b) Decreasing
Explanation: Freshwater sources are depleting due to overuse, pollution, and climate change, posing a significant threat to global water security.
Descriptive Questions
2. Explain the distribution of water on the global level.
Water on Earth is unevenly distributed among different reservoirs:
- Oceans: Hold about 90% of Earth’s water, mostly saline.
- Glaciers and Ice Caps: Store approximately 2% of the total water, mainly as freshwater.
- Groundwater: Makes up around 1% and is a significant source of freshwater.
- Rivers, Lakes, and Streams: Constitute a very small fraction but are vital for human consumption and ecosystems.
- Atmosphere: Contains a minimal amount in the form of water vapor.
3. How raw water treatment is done for municipal water supply?
Raw water treatment involves several stages:
- Screening: Removes large debris such as leaves and trash.
- Coagulation and Flocculation: Chemicals like alum are added to form clumps of dirt and particles.
- Sedimentation: Heavy particles settle at the bottom, leaving cleaner water at the top.
- Filtration: Water passes through sand and gravel to remove smaller particles.
- Disinfection: Chlorine, ozone, or UV light is used to kill harmful bacteria and viruses.
4. Why does water dissolve many substances, and why is it called a universal solvent?
Water is called the universal solvent because:
- Polarity: Water molecules have a polar nature, allowing them to interact with various ions and polar compounds.
- Hydrogen Bonding: It forms hydrogen bonds with solutes, breaking them apart into their components.
This ability makes water vital for life, as it dissolves nutrients, gases, and waste products in biological systems.
5. Evaluate the strain on freshwater availability by agriculture and industry.
- Agriculture: Accounts for about 70% of global freshwater use. Irrigation and crop production require massive amounts of water, often leading to over-extraction and depletion of aquifers.
- Industry: Consumes significant water for manufacturing, cooling, and cleaning processes, polluting freshwater sources with chemicals and waste.
These demands reduce freshwater availability for domestic and ecological purposes.
6. Suggest some measures to ensure the preservation of water reservoirs.
- Efficient Irrigation: Use drip or sprinkler systems to reduce water wastage.
- Pollution Control: Prevent industrial effluents and agricultural runoff from entering water bodies.
- Rainwater Harvesting: Collect and store rainwater for future use.
- Public Awareness: Educate people about the importance of conserving water.
- Government Policies: Enforce strict regulations on water usage and pollution.
7. Evaluate the impact of pollutants on the ecosystem.
Pollutants like heavy metals, pesticides, and industrial waste harm ecosystems in the following ways:
- Aquatic Life: Toxic substances cause diseases and death in fish and other aquatic organisms.
- Eutrophication: Excess nutrients lead to algal blooms, depleting oxygen levels and killing aquatic species.
- Bioaccumulation: Harmful chemicals accumulate in organisms, moving up the food chain and affecting humans.
- Water Quality: Pollutants degrade water quality, making it unsafe for drinking and agriculture.
