Past paper questions

Question 1

Conversion of MJ-kWh

Answer 1

1kWh=0.2778 MJ

Question 2

Conversion of kWh to MJ

Answer 2

1MJ=3.6KWh
1kW=1000W=1000Js
1kWh=1000* 60* 60=3,600,000 J=3.6MJ

Question 3

Total generation (MJ) Equation

Answer 3

=Generating capacity (MW) x Load x 8760 x 3600

Question 4

Total generation (kWh) Equation

Answer 4

=Generating capacity (MW) x Load x 8760 x 1000

Question 5

Mixing ratio equation

Answer 5

= Volume mixing ration x (Mx/Md)

Question 6

Total mass of gas in atmosphere equation

Answer 6

=Mass mixing ratio x mass of the atmosphere

Question 7

Atospheric growth rate - Equation

Answer 7

Difference in mixing ratio/ difference in time

Question 8

Features of N₂O (Nitrous Oxide)

Answer 8

A long-lived greenhouse gas

Mainly emitted from agriculture (fertilizers), waste management, and some industrial processes

Lifetime: ~121 years

Not directly toxic to humans at environmental levels

Question 9

Features of NOₓ (Nitric Oxide NO + Nitrogen Dioxide NO₂)

Answer 9

Short-lived atmospheric pollutants

Emitted from combustion (vehicles, power plants, industry)

Lifetime: Hours to days

Strongly affects air quality, ecosystems, and human health

Question 10

Difference between impacts of NOx and N2O

Answer 10

• N₂O is a global climate threat with long-lasting warming effects and contributions to stratospheric ozone depletion, but low direct toxicity.
• NOₓ is a regional air pollutant with immediate and serious health impacts, as well as significant damage to ecosystems through acidification and ozone formation.

Question 11

Policy responses difference N2O and NOx

Answer 11

N₂O: focus on long-term mitigation via agriculture and fertilizer management

NOₓ: target urban pollution control, clean energy, and transport systems to protect human health and ecosystems

Question 12

What are the primary sources of N₂O and NOₓ?

Answer 12

N₂O: Agriculture (fertilizers), waste, industry

NOₓ: Combustion engines, power plants, industrial processes

Question 13

What is the atmospheric lifetime of N₂O vs NOₓ?

Answer 13

N₂O: ~121 years (long-lived, globally mixed)

NOₓ: Hours to days (short-lived, local/regional)

Question 14

How do N₂O and NOₓ affect the climate?

Answer 14

N₂O: Strong greenhouse gas, causes global warming and ozone depletion

NOₓ: Indirect climate effects — warms via ozone, cools by reducing methane

Question 15

What are the health impacts of N₂O vs NOₓ?

Answer 15

N₂O: Minimal at environmental levels

NOₓ: Severe — causes respiratory issues, asthma, cardiovascular problems

Question 16

How do these gases affect ecosystems?

N2O and NOx

Answer 16

N₂O: Affects climate and stratospheric ozone (global)

NOₓ: Causes acid rain, eutrophication, ozone damage (regional)

Question 17

Which gas is more relevant for regional air pollution?

Answer 17

NOₓ, due to its short lifetime and direct health/ecosystem effects

Question 18

Why is N₂O more important for long-term climate policy?

Answer 18

Because of its long atmospheric lifetime, it accumulates and contributes significantly to global warming and ozone layer depletion.

Question 19

How do NOₓ emissions influence methane and ozone levels?

Answer 19

Reduce methane (cooling effect)

Increase ozone (warming and toxic effect)

Question 20

What is the difference between greenhouse gases and air pollutants?

Answer 20

Greenhouse gases (GHGs) like CO₂, CH₄, and N₂O trap infrared radiation in the atmosphere, contributing to the greenhouse effect and global warming.

Air pollutants like NOx, VOCs, and particulate matter directly harm human health and the environment, often causing respiratory issues and smog.

Question 21

How do NOx and VOCs contribute to the formation of tropospheric ozone?

Answer 21

NOx (NO and NO₂) reacts with sunlight to produce ozone (O₃) through photolysis and subsequent reactions.

VOCs react with NO to form peroxy radicals, which then form NO₂, increasing ozone production in the presence of sunlight.

Question 22

What is the formula to calculate the total mass of a substance accumulated over time?

Answer 22

Totalmassaccumulated=Emissionrate×Timeperiod

Question 23

How do human activities alter the global nitrogen cycle and contribute to atmospheric pollution?

Answer 23

Industrial activities (e.g., fossil fuel burning) release NOx and N₂O, which contribute to air pollution and acid rain.

Agriculture adds excessive nitrogen to soils through fertilizers and manure, leading to runoff and eutrophication in water bodies.

N₂O is a potent greenhouse gas that contributes to global warming.

Question 24

What is the formula for calculating the concentration of a substance at steady-state in the atmosphere?

Answer 24

C=Ext/Atmospheric volume

Question 25

What are the primary sources of NOx and VOCs in the atmosphere?

Answer 25

NOx: Primarily produced by fossil fuel combustion (e.g., vehicles, power plants) and industrial processes. VOCs: Emitted from vehicle exhaust, solvents, industrial emissions, and biogenic sources like plants.

Question 26

How does acid deposition occur and what are its effects?

Answer 26

Acid deposition occurs when SO₂ and NOx dissolve in water vapor, forming sulfuric acid (H₂SO₄) and nitric acid (HNO₃), which fall as acid rain, snow, or dust. Effects include soil acidification, damage to aquatic ecosystems, forest degradation, and corrosion of buildings.

Question 27

How does nitrous oxide (N₂O) contribute to both global warming and ozone depletion?

Answer 27

Global warming: N₂O is a potent greenhouse gas that traps heat in the atmosphere. Ozone depletion: N₂O breaks down into nitrogen oxides (NOx) in the stratosphere, which can damage the ozone layer.