Chemistry of the environment
Environmental Issues
Acidity of Water
- • pH Levels
- • Most Acidic Sample (pH 2)
- • Least Acidic Sample (pH 6)
Gas Testing and Collection
- • Carbon Dioxide Detection
- • Gas Collection Methods
Global Warming
- • Greenhouse Gases
- • Causes
- • Mitigation Strategies
Pollution
- • Air Pollution
- • Water Pollution
- • Acid Rain
Water Treatment
- • Filtration
- • Coagulation
- • Sedimentation
- • Chlorination
Fertilizers
- • Types
- • Nitrogen Calculation
- • Environmental Impact
Understanding Acidity, Gas Testing, Global Warming, Pollution, and Water Treatment
Acidity of Water
pH Levels
The pH scale measures how acidic or basic a solution is, ranging from 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic. The pH level depends on the concentration of hydrogen ions (H⁺) present; the more H⁺ ions, the more acidic the solution, and the lower its pH.
Most Acidic Sample (pH 2)
A sample with a pH of 2 is highly acidic, similar to lemon juice or stomach acid. Such acidity can harm aquatic life and corrode infrastructure, making it important to monitor in environmental contexts.
Least Acidic Sample (pH 6)
A sample with a pH of 6 is slightly acidic, typical of natural rainwater. This level is generally safe for life but can indicate environmental changes or pollution if consistently monitored.
Gas Testing and Collection
Carbon Dioxide Detection
Reaction with Limewater
Carbon dioxide (CO₂) is detected by bubbling it through limewater (calcium hydroxide solution). A reaction occurs, turning the limewater milky due to the formation of calcium carbonate (CaCO₃).
Formation of Calcium Carbonate
The reaction can be represented as:
CO₂ (g) + Ca(OH)₂ (aq) → CaCO₃ (s) + H₂O (l)
This produces a milky white precipitate, confirming CO₂ presence.
Gas Collection Methods
Gases produced in reactions can be collected using the inverted test tube or gas jar methods. Both involve displacing water in a container to trap gases, which works well for gases like CO₂ that are insoluble in water.
Global Warming
Greenhouse Gases
Carbon Dioxide
CO₂ is a key greenhouse gas contributing to global warming, released naturally through respiration and volcanic activity, and by human activities like burning fossil fuels. Increased CO₂ enhances the greenhouse effect, trapping more heat.
Methane
Methane (CH₄), while present in smaller amounts than CO₂, is more effective at trapping heat. Its sources include wetlands, agriculture, and waste decomposition.
Causes
Deforestation
Deforestation releases stored carbon from trees, exacerbating CO₂ levels and global warming.
Fossil Fuel Combustion
Burning coal, oil, and natural gas for energy and transportation releases large quantities of CO₂, driving climate change.
Mitigation Strategies
Alternative Fuels
Transitioning to renewable energy like solar, wind, and biofuels can significantly reduce greenhouse gas emissions.
Energy Efficiency
Using energy-efficient technologies reduces fossil fuel consumption and emissions, helping combat global warming.
Pollution
Air Pollution
Motor Vehicles
Vehicles emit pollutants like carbon monoxide and nitrogen oxides, contributing to air pollution. Catalytic converters help reduce these emissions by converting harmful gases into less dangerous substances.
Carbon Monoxide
CO is a dangerous, colorless gas produced by incomplete combustion, posing serious health risks.
Nitrogen Oxides
NOâ‚“ gases, produced during combustion, contribute to smog and acid rain, harming both health and the environment.
Sulfur Dioxide
SO₂, released from burning fossil fuels, forms acid rain and causes respiratory problems.
Water Pollution
Agricultural Runoff
Agricultural runoff leads to nutrient pollution, causing algal blooms and harming aquatic life.
Industrial Waste
Industrial waste contaminates water bodies with toxins, posing health risks to humans and wildlife.
Sewage
Sewage pollution degrades water quality and spreads waterborne diseases.
Plastic Waste
Non-biodegradable plastics harm marine life and contribute to waterway pollution.
Acid Rain
Formation
Acid rain forms when SO₂ and NOâ‚“ gases react with water vapor, creating acidic precipitation.
Environmental Impact
Acid rain damages forests, acidifies water bodies, and corrodes buildings and infrastructure.
Water Treatment
Filtration
Filtration removes large particles from water by passing it through layers of sand, which may also contain microbes that help purify the water.
Coagulation
Coagulation involves adding chemicals like aluminum sulfate to clump small particles into larger aggregates, making them easier to remove.
Sedimentation
In sedimentation, these aggregates settle at the bottom of a tank, separating from the clearer water above.
Chlorination
Chlorination disinfects water by adding chlorine to kill bacteria and viruses, ensuring safe drinking water.
Fertilizers
Types
Ammonium Nitrate
This common nitrogenous fertilizer provides plants with nitrogen, promoting growth and increasing yields.
Ammonium Sulfate
Ammonium sulfate supplies nitrogen and sulfur, particularly useful in sulfur-deficient or alkaline soils.
Environmental Impact
Leaching
Leaching occurs when excess fertilizers are washed into water bodies, contaminating them and depleting soil nutrients.
Eutrophication
Eutrophication leads to algal blooms that deplete oxygen in water, creating dead zones harmful to aquatic life.
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1. Cooling and Volume Reduction
a. The apparatus is allowed to cool to room temperature before measuring the final volume to ensure the gas returns to normal temperature conditions, making the volume measurement accurate.b. Percentage volume reduction:
(200 cm³ - 157 cm³) / 200 cm³ x 100% = 21.5%
c. The volume change occurs because oxygen in the air reacts with hot copper, reducing the amount of gas in the system.
d. An observation supporting the explanation in c is that the copper slowly turns black, indicating a chemical reaction.
e. Chemical reaction equation:
2Cu + O₂ → 2CuO
f. The main residual gas at the end of the experiment is nitrogen.
2. Oxygen Atom and Molecule
a. Electronic configuration of oxygen atom: 1s² 2s² 2p⁴b. An oxygen atom has:
- 8 protons
- 8 neutrons
- 8 electrons
c. Oxygen molecules are diatomic, meaning they consist of two oxygen atoms bonded to form one molecule.
d. Oxygen molecule diagram (outer shell):
O=O
Bond type: double covalent bond
3. Air Composition and Pollution
a. Air is a mixture of elements and compounds, including nitrogen, oxygen, argon, carbon dioxide, and water vapor.b. The percentage of carbon dioxide in the atmosphere remains relatively stable due to the natural balance between CO₂ sources and sinks.
c. Power plants are considered a major cause of acid rain because they release pollutants like sulfur dioxide and nitrogen oxides that react with atmospheric water to form acids.
4. Water Properties and Treatment
Water is essential for all life on Earth. It is the most abundant substance on Earth. Water is not only used for drinking and washing but also:- in chemical reactions, for example in the production of ethanol from ethene
- as a solvent to dissolve things
- as a coolant in some chemical processes.
For us to drink it, water must be relatively pure. To make water drinkable, any undissolved solids are removed through filtration beds. Aluminum sulfate is added to remove small clay particles and chlorine is added to kill bacteria.
Water is continuously monitored because certain substances eventually find their way into the water supply.
5. Pollution and Water Purification
a. Pollution refers to the introduction of harmful substances into air and water that can damage the environment and living beings' health.b. i. An air pollutant produced from burning coal: sulfur dioxide.
ii. A different air pollutant produced from burning gasoline in car engines: carbon monoxide.
c. i. Distillation would produce the purest water from river water as this process separates water from all contaminants, including dissolved substances.
ii. Filtration is actually used to produce drinking water from river water. Although distillation produces purer water, filtration is more practical and cost-effective for large-scale water treatment.
6. Greenhouse Effect and Global Warming
a. Another greenhouse gas besides carbon dioxide: methane.b. The greenhouse effect refers to the warming of Earth's atmosphere caused by certain gases trapping solar heat. This is similar to how a greenhouse retains heat for plants. These gases, like CO2, absorb and re-emit infrared radiation, increasing Earth's average temperature.
c. i. The general trend shown in the graph since 1860 is an increase in average global air temperature, particularly sharp since around 1920.
ii. The cause of this trend is likely the increase in greenhouse gas emissions, especially CO2, due to human activities such as industrialization, fossil fuel use, and deforestation. These factors have increased atmospheric greenhouse gas concentrations, amplifying the greenhouse effect and causing global warming.
