Chapter 12

PARAMOUNT SCHOOL SYSTEM

Subject: Chemistry – I

Unit 12: Environmental Chemistry – Water

CONCEPT ASSESSMENT EXERCISE 12.1

1. List some water borne diseases.

Some water borne diseases:

  • Cholera
  • Typhoid
  • Dysentery
  • Hepatitis

2. List sources of water borne diseases.

Sources of Water-Borne Diseases:

  1. Contaminated drinking water
  2. Improperly treated sewage
  3. Agricultural runoff containing fertilizers and pesticides
  4. Industrial discharge into water bodies
  5. Poor sanitation and hygiene practices

3. List steps used in raw water treatment.

Raw water is treated in a municipal water purification plant to make it fit for drinking and domestic purposes. The various stages in this treatment are:

Sedimentation:

In this process, water is allowed to stand in a reservoir. The suspended matter sinks to the bottom, effectively removing large particles from the water.

Coagulation:

Water is treated with slaked lime and alum. These materials react to form a gelatinous mass of aluminum hydroxide.

3Ca (OH)2 (aq) + Al2 (SO4)3 (aq) → 2Al (OH)3 (s) + 3CaSO4 (aq)

The aluminum hydroxide carries down dirt particles and bacteria, helping to purify the water.

Filtration:

The water is then filtered through sand and gravel to remove smaller particles. Sometimes, it is also filtered through charcoal to remove colored and odorous compounds.

Chlorination:

In the final step, chlorine is added to kill any remaining bacteria. Chlorine reacts with water to form hypochlorous acid (HClO), which kills bacteria.

Cl2 (aq) + H2O(l) → HClO(aq) + H+ (aq) + Cl− (aq)

REVIEW QUESTIONS

1. Encircle the correct answer.

  1. Which of the followings is not a water borne disease?

a) hepatitis b) typhoid C) dysentery d) anemia

  1. Which human activity results in contamination of water bodies?

a) livestock waste b) pesticides c) septic tanks d) all of these

  1. pH of distilled water is:

a) 7 b) Less than 7 c) Greater than 7 d) None of these

  1. Anhydrous copper (II) sulphate is _____________solid.

a) blue b) white c) yellow d) None of these

2. Give short answer.

  1. List the impurities present in rain water.

The impurities present in rainwater are:

  • Oxygen
  • Nitrogen
  • Carbon dioxide
  • Dust particles
  • Nitric acid (during thunderstorms)
  • Minerals (dissolved from rocks and soils)
  • Substances from decaying plants and animals.
  1. List toxic substances present in household wastes.

Toxic substances present in household wastes:

  • Soaps and detergents
  • Paints
  • Oil
  • Chemical contents (in household water)
  • Bacterial contents
  1. In what ways, industrial wastes pollute water.
  2. Ways Industrial Wastes Pollute Water:
  3. Industrial waste contains highly toxic compounds and heavy metals.
  4. Common toxic heavy metals include Pd, Cd, Cr, Hg, As, Sb.
  5. Leather tannery water contains high levels of chromium (VI) salts.
  6. Chromium (VI) ions are highly toxic and can cause cancer.
  7. What is water pollution?

Water pollution is the contamination of water bodies due to human activities such as household waste, agricultural waste, surface waste, pesticides, oil leaks, detergents, septic tanks, petroleum, and natural gas production.

  1. List some waterborne diseases.

Some water borne diseases:

  • Cholera
  • Typhoid
  • Dysentery
  • Hepatitis
  1. What are pathogenic microorganisms?

An organism of microscopic size, usually a bacteria or virus, that causes disease. These organisms are transmitted through food, water and direct contact. These organism may cause typhoid fever, dysentery and hepatitis.

3. How does tap water differ from distilled water?

Tap Water Distilled Water
Comes from natural sources like streams, rivers, lakes, reservoirs, and groundwater. Made by boiling and condensing water.
Contains minerals and some impurities. Free of impurities and contaminants.
Treated to be safe for drinking. Lacks essential minerals.
Used for household and general purposes. Used in laboratories for specific tasks.
Has normal electrical conductivity. Has very low electrical conductivity.

4. Why are municipal water supplies treated with aluminium sulphate?

Municipal water supplies are treated with aluminum sulfate for coagulation. When aluminum sulfate is added to water, it reacts to form a gelatinous mass of aluminum hydroxide, which helps to carry down dirt particles and bacteria, making the water clearer and safer for use.

5. What are some health effects of biological contamination of water?

Some health effects of biological contamination of water are:

  1. Dysentery causes severe abdominal cramps and diarrhea.
  2. Cholera leads to severe diarrhea and dehydration.
  3. Typhoid results in high fever and irregular pulse.
  4. Hepatitis causes liver inflammation and can lead to jaundice.

6. Identify the negative effects of water pollutants on life.

Negative effects of water pollutants:

  1. Pollutants can kill aquatic life.
  2. Heavy metals in water can cause serious health issues like neurological problems and cancer.
  3. Biological contaminants can cause diseases like cholera, typhoid, and hepatitis.
  4. Excess nitrates and phosphates can lead to harmful algae blooms.
  5. Polluted water can become unsafe for drinking.

7. Water scarcity is an important issue in Pakistan. Give your comments on it.

Water scarcity in Pakistan is a serious problem due to:

  1. Growing population needs more water.
  2. Overuse of water faster than it can be replenished.
  3. Climate change causing unpredictable weather.
  4. Pollution making water unsafe.
  5. Poor water management and inefficient practices.

8. What are fertilizers?

Fertilizers are substances that provide essential elements for plant growth, mainly nitrogen (N), phosphorus (P), and potassium (K). They dissolve in water to give nutrients to plants in a readily available form.

THINK TANK

9. Public health depends on water quality. Give arguments.

Clean water is very important for public health because:

  1. Polluted water may contain harmful substances such as heavy metals and chemicals that affect health.
  2. Ensuring water quality helps prevent outbreaks of diseases and protects public health.
  3. Safe and clean water supports overall health and well-being by reducing the risk of waterborne diseases.
  4. Contaminated water can carry harmful bacteria, viruses, and pathogens that cause illness.

10. How chemistry helps maintain a clean swimming pool? Explain.

Chemistry helps keep swimming pools clean through aeration and chlorination. Aeration adds oxygen to the water, which helps get rid of contaminants. Chlorination adds chlorine to kill harmful bacteria and viruses. Together, these treatments make sure the pool water stays safe for swimming.

11. It is advisable to wash hands well with soap after using bathrooms. Evaluate it.

Washing hands well with soap after using the bathroom is important because it helps remove germs and bacteria that could cause illnesses. Proper hand washing reduces the risk of spreading diseases such as diarrhea, dysentery, and hepatitis, which can be transmitted through contaminated surfaces and water.