Chemistry Topic 1.1 & 1.2 Mini-Test

Explain how greenhouse gases contribute to the greenhouse effect

Greenhouse gases such as carbon dioxide and methane absorb infrared radiation emitted from the Earth’s surface and re-radiate it back toward Earth. This traps heat within the atmosphere and maintains Earth’s temperature.

- IR radiation enters atmosphere

- Earth emits infrared radiation

- Greenhouse gases absorb IR radiation

- Heat is re-radiated

Greenhouse gases absorb and re-radiate infrared radiation, trapping thermal energy in the atmosphere.

What are anthropogenic increases in greenhouse gases?

Anthropogenic increases are increases caused by human activities such as burning fossil fuels, deforestation, agriculture, and industrial processes.

- Human-caused

- Increased CO₂ and methane

- Disrupts Earth’s thermal balance

Anthropogenic emissions increase atmospheric greenhouse gas concentrations.

Explain one consequence of anthropogenic increases in greenhouse gases.

Increased greenhouse gases enhance the greenhouse effect, causing global warming. This leads to melting glaciers, rising sea levels, and disruption of ecosystems.

- More heat trapped

- Temperature rises

- Environmental impacts

Enhanced greenhouse warming contributes to climate change and environmental disruption.

How do you write a conclusion from a graph?

State the trend, relationship, and evidence shown in the graph.

- Mention increase/decrease

- Mention positive/negative relationship

- Refer to variables

“As ___ increases, ___ increases/decreases, indicating a positive/negative relationship.”

Write the equation for formation of carbonic acid in water.

Carbon dioxide reacts with water to form carbonic acid.

- CO₂ dissolves in ocean

- Carbonic acid forms

Equation:

CO₂(g) + H₂O(l) ⇌ H₂CO₃(aq)

Absorbed atmospheric carbon dioxide forms carbonic acid in seawater.

Write the first ionisation equation of carbonic acid.

Carbonic acid partially ionises to produce hydrogen ions and hydrogen carbonate ions.

- Produces H⁺

- Lowers pH

Equation:

H₂CO₃(aq) ⇌ H⁺(aq) + HCO₃⁻(aq)

Carbonic acid ionises to increase hydrogen ion concentration.

Write the second ionisation equation of carbonic acid.

Hydrogen carbonate ions further ionise to produce additional hydrogen ions.

- Second ionisation

- Further increases acidity

Equation:

HCO₃⁻(aq) ⇌ H⁺(aq) + CO₃²⁻(aq)

Further ionisation contributes additional hydrogen ions.

Explain how ocean acidification affects marine organisms.

Increased hydrogen ion concentration lowers ocean pH and causes calcium carbonate shells and skeletons to dissolve.

- Lower pH

- Calcium carbonate dissolves

- Coral/shell damage

Equation:

CaCO₃(s) + 2H⁺(aq) → Ca²⁺(aq) + CO₂(g) + H₂O(l)

Acidic conditions dissolve calcium carbonate structures.

What is the equation for calculating pH?

pH is calculated using the negative logarithm of hydrogen ion concentration.

- Measures acidity

- Lower pH = more acidic

Equation:

pH = -log[H⁺]

pH is inversely related to hydrogen ion concentration.

How do you calculate hydrogen ion concentration from pH?

Rearrange the pH equation by using the inverse logarithm.

- Convert pH into concentration

- Use powers of 10

Equation:

[H⁺] = 10^(-pH)

Hydrogen ion concentration is determined using the inverse logarithmic relationship.

How do you calculate concentration of a fully ionising diprotic acid?

A fully ionising diprotic acid releases two hydrogen ions per molecule.

- 2 H⁺ per acid molecule

- Divide H⁺ concentration by 2

Equation:

[H⁺] = 2[acid]

A diprotic acid produces two moles of hydrogen ions per mole of acid.

How are nitrogen oxides formed in engines?

High temperatures in engines cause nitrogen and oxygen in air to react and form nitrogen monoxide.

- High temperature reaction

- Occurs in engines/furnaces

Equation:

N₂(g) + O₂(g) → 2NO(g)

High combustion temperatures enable atmospheric nitrogen and oxygen to react.

How is nitrogen dioxide formed?

Nitrogen monoxide reacts with oxygen to form nitrogen dioxide.

- Secondary reaction

- Produces NO₂ pollutant

Equation:

2NO(g) + O₂(g) → 2NO₂(g)

Nitrogen monoxide undergoes oxidation to form nitrogen dioxide.

How does photochemical smog form?

Sunlight breaks down nitrogen dioxide to form oxygen atoms, which react with oxygen gas to produce ozone.

- Requires sunlight

- Produces tropospheric ozone

Equations:

NO₂ + sunlight → NO + O

O + O₂ → O₃

Photochemical reactions involving nitrogen oxides produce tropospheric ozone.

What are harmful effects of photochemical smog?

Photochemical smog causes respiratory irritation, damages plants, reduces visibility, and contributes to poor air quality.

- Lung irritation

- Environmental damage

- Ozone pollutant

Tropospheric ozone and nitrogen oxides negatively affect human health and ecosystems.

How do catalytic converters reduce pollution?

Catalytic converters convert harmful nitrogen oxides and carbon monoxide into less harmful gases.

- Reduces NOₓ

- Oxidises CO

- Produces safer gases

Equations:

2NO → N₂ + O₂

2CO + O₂ → 2CO₂

Catalytic converters reduce harmful vehicle emissions through redox reactions.