Chemistry Of The Environment

Question 1

Chemical Tests for the Presence of Water

Answer 1

1. Anhydrous Cobalt(II) Chloride:

Test: Changes color from blue to pink in presence of water vapor or liquid water.

Indication: Color change from blue to pink signals the presence of water.

2. Anhydrous Copper(II) Sulfate:

Test: Turns from white to blue upon reaction with water.

Indication: Blue coloration indicates the presence of water.

Question 2

Testing Purity & Why do we use distilled water?

Answer 2

Melting Point:
Pure water: Melts at 0°C under standard atmospheric pressure.
Deviation from 0°C suggests impurities in water.

Boiling Point:
Pure water: Boils at 100°C under standard atmospheric pressure.
Deviation from 100°C during boiling may indicate impurities.

Use of Distilled Water:
Distilled water preferred in practical chemistry.
Contains fewer chemical impurities compared to tap water.

Question 3

Substances Found in Natural Water Sources: Beneficial & Potentially Harmful (6)

Treatment of Water (3)

Answer 3

Substances Found in Natural Water Sources:

Beneficial Substances:

Dissolved Oxygen: Supports aquatic life.

Certain Metal Compounds: Provide essential minerals.

Potentially Harmful Substances:

Certain Metal Compounds: Toxic.

Plastics: Harm aquatic life.
Sewage: Contains harmful microbes.

Nitrates from Fertilizers: Cause deoxygenation.

Phosphates from Fertilizers and Detergents: Cause damage to aquatic life.

Treatment of Domestic Water Supply:

Sedimentation and Filtration: Remove solids from water.

Use of Carbon: Remove tastes and odors.

Chlorination: Kill microbes to ensure water safety.

Question 4

Fertilizers and how they benefit plants

Answer 4

Ammonium salts and nitrates are utilized as fertilizers.

NPK fertilizers provide essential elements for improved plant growth:

Nitrogen (N): Stimulates leaf and stem growth, enhances chlorophyll production.

Phosphorus (P): Promotes root development, aids in flower and fruit formation.

Potassium (K): Enhances overall plant health, regulates water uptake and photosynthesis.

Question 5

Composition of Clean Dry Air (4)

Sources of Air Pollutants (5)

Effects of Air Pollutants (5)

Greenhouse gases & Global Warmimg Mechanism

Answer 5

Composition of Clean, Dry Air:

Approximately 78% nitrogen

About 21% oxygen

Remainder as a mixture of noble gases and carbon dioxide (CO2)

Sources of Air Pollutants:

Carbon dioxide: Complete combustion of carbon-containing fuels.

Carbon monoxide (CO) and Particulates: Incomplete combustion of carbon-containing fuels.

Methane (CH4): Decomposition of vegetation and waste gases from animal digestion.

Oxides of Nitrogen (NOx): Car engines.

Sulfur Dioxide (SO2): Combustion of fossil fuels containing sulfur compounds.

Adverse Effects of Air Pollutants:

Carbon Dioxide (CO2): Contributes to increased global warming and climate change.

Carbon Monoxide (CO): Toxic gas harmful to human health.
Particulates: Increase the risk of respiratory problems and cancer.

Methane (CH4): Contributes to increased global warming and climate change.

Oxides of Nitrogen (NOx): Contribute to acid rain, photochemical smog, and respiratory problems.

Sulfur Dioxide (SO2): Contributes to acid rain.

Greenhouse Gases and Global Warming Mechanism:
Absorb thermal energy emitted by the Earth’s surface.

Reduce loss of thermal energy from Earth to space, trapping heat within the atmosphere.

Question 6

Strategies to reduce Climate change & Acid Rain

Photosynthesis Word & Symbol Equation

Answer 6

(a) Climate Change:

Planting trees for carbon dioxide absorption.

Reducing livestock farming to lower methane emissions.

Promoting energy efficiency and transitioning to cleaner alternatives to decrease fossil fuel use.

Increasing use of hydrogen and renewable energy sources like wind and solar power.

(b) Acid Rain:

Installing catalytic converters in vehicles to reduce nitrogen oxide emissions.

Using low-sulfur fuels and flue gas desulfurization with calcium oxide to decrease sulfur dioxide emissions.

Catalytic converters remove oxides of nitrogen in car engines through reactions like :
2NO₂ + 4CO → N₂ + 4CO₂

Photosynthesis Equations:

Word Equation:
Carbon dioxide + Water →
Glucose + Oxygen

Symbol Equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂