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Chemistry: Environmental Systems - Air Pollutants, Atmospheric Chemistry, and Carbon Footprints

Grade 8IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Composition of the Atmosphere: The Earth's atmosphere is primarily composed of Nitrogen (78%78\%), Oxygen (21%21\%), Argon (0.9%0.9\%), and Carbon Dioxide (0.04%0.04\%), along with trace gases and water vapor.

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Primary vs. Secondary Pollutants: Primary pollutants are emitted directly from a source (e.g., COCO from car exhausts), while secondary pollutants form in the atmosphere through chemical reactions (e.g., H2SO4H_2SO_4 in acid rain).

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The Greenhouse Effect: Greenhouse gases like Carbon Dioxide (CO2CO_2), Methane (CH4CH_4), and Nitrous Oxide (N2ON_2O) trap infrared radiation, maintaining Earth's temperature but leading to global warming when in excess.

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Acid Rain: Formed when Sulfur Dioxide (SO2SO_2) and Nitrogen Oxides (NOxNO_x) react with water (H2OH_2O), oxygen, and other chemicals in the atmosphere to form sulfuric and nitric acids.

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Carbon Footprint: The total amount of greenhouse gases, primarily CO2CO_2, released into the atmosphere by a particular human activity, organization, or community.

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Incomplete Combustion: Occurs when there is insufficient oxygen, leading to the formation of Carbon Monoxide (COCO) and soot (CC) instead of Carbon Dioxide (CO2CO_2).

📐Formulae

S(s)+O2(g)→SO2(g)S_{(s)} + O_{2(g)} \rightarrow SO_{2(g)}

SO2(g)+H2O(l)→H2SO3(aq)SO_{2(g)} + H_2O_{(l)} \rightarrow H_2SO_{3(aq)}

2C(s)+O2(g)→2CO(g)2C_{(s)} + O_{2(g)} \rightarrow 2CO_{(g)}

CH4(g)+2O2(g)→CO2(g)+2H2O(l)CH_{4(g)} + 2O_{2(g)} \rightarrow CO_{2(g)} + 2H_2O_{(l)}

N2(g)+O2(g)→2NO(g)N_{2(g)} + O_{2(g)} \rightarrow 2NO_{(g)}

💡Examples

Problem 1:

A factory reduces its monthly carbon emissions from 5500 kg5500 \text{ kg} to 3275 kg3275 \text{ kg} by installing solar panels. Calculate the total reduction in CO2CO_2 emissions using vertical subtraction.

Solution:

5500−32752225\begin{array}{r} 5500 \\ -3275 \\ \hline 2225 \end{array}

Explanation:

The total reduction is calculated by subtracting the new emission level from the original level. The factory saved 2225 kg2225 \text{ kg} of CO2CO_2 per month.

Problem 2:

Write and balance the chemical equation for the complete combustion of Propane (C3H8C_3H_8).

Solution:

C3H8+5O2→3CO2+4H2OC_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O

Explanation:

In complete combustion, a hydrocarbon reacts with oxygen (O2O_2) to produce carbon dioxide (CO2CO_2) and water (H2OH_2O). We balance the carbons first (33), then hydrogens (8÷2=48 \div 2 = 4), and finally the oxygens (3×2+4=103 \times 2 + 4 = 10, so 10÷2=510 \div 2 = 5).

Problem 3:

Identify the pollutant formed when Nitrogen (N2N_2) and Oxygen (O2O_2) react at high temperatures inside a car engine.

Solution:

N2+O2→2NON_2 + O_2 \rightarrow 2NO

Explanation:

Nitrogen is usually inert, but at the very high temperatures found in internal combustion engines, it reacts with oxygen to form Nitrogen Monoxide (NONO), which later oxidizes to Nitrogen Dioxide (NO2NO_2), a major contributor to photochemical smog and acid rain.