IB Chemistry Reactivity 1.3 - Energy from Fuels Flashcards

This set of vocabulary flashcards covers IB Chemistry SL/HL Topic R1.3, focusing on combustion types, fossil fuel comparisons, biofuel sustainability, and the mechanisms of fuel cells.

Combustion

A rapid exothermic reaction between a substance and oxygen; the primary process for extracting energy from fuels.

Complete Combustion

Combustion in excess oxygen where all carbon is converted to $CO_{2}$ and all hydrogen to $H_{2}O$, releasing maximum energy.

Incomplete Combustion

Combustion in a limited oxygen supply where not all carbon is fully oxidised, resulting in the formation of carbon monoxide ($CO$) or carbon (soot) and lower energy output.

Carbon Monoxide ($CO$)

A toxic product of incomplete combustion that binds to haemoglobin approximately $240 \times$ more strongly than $O_{2}$, preventing oxygen transport.

Carbon (Soot)

Fine particulates ($PM_{2.5}$) produced during limited oxygen combustion that can penetrate deep into lung tissue, linked to respiratory and cardiovascular disease.

C:H Ratio

The ratio of carbon to hydrogen atoms; larger hydrocarbons with a higher ratio require more oxygen per molecule and have a greater tendency for incomplete combustion.

Fossil Fuels

Non-renewable energy sources (coal, crude oil, natural gas) formed over millions of years from compressed organic matter.

Coal

A fossil fuel composed of complex carbon compounds with high carbon content; it produces the highest $CO_{2}$ emissions per unit of energy ($\text{~}90\text{ g }CO_{2}\text{ per MJ}$).

Crude Oil

A mixture of liquid hydrocarbons (mainly $C_{5}$–$C_{12}$) with moderate $CO_{2}$ emissions per unit of energy ($\text{~}70\text{ g }CO_{2}\text{ per MJ}$).

Natural Gas

Fossil fuel mainly consisting of methane ($CH_{4}$); it is the cleanest fossil fuel with the lowest $CO_{2}$ emissions per unit of energy ($\text{~}50\text{ g }CO_{2}\text{ per MJ}$).

Greenhouse Effect

Process where gases like $CO_{2}$ absorb infrared radiation emitted by the Earth and re-emit it in all directions, warming the lower atmosphere.

Dipole Moment Change

The mechanism allowing $CO_{2}$ to absorb infrared radiation via asymmetric stretching and bending vibrations.

Biofuels

Fuels produced from the biological fixation of carbon over a short period of time through photosynthesis.

Photosynthesis

The process by which crops absorb $CO_{2}$, represented by the equation $6CO_{2}(g) + 6H_{2}O(l) \rightarrow C_{6}H_{12}O_{6}(aq) + 6O_{2}(g)$.

Bioethanol

A biofuel produced by the fermentation of sugars or starch from crops like sugar cane, corn, or wheat.

Biodiesel

A biofuel produced by reacting plant oils (triglycerides) with methanol through transesterification.

Carbon Neutral

A description of fuels where the $CO_{2}$ released during combustion is equal to the $CO_{2}$ absorbed from the atmosphere during growth, resulting in approximately zero net addition.

Fuel Cell

A device that converts chemical energy from a fuel directly into electrical energy through electrochemical reactions without first converting it to heat.

Carnot Efficiency

The fundamental thermodynamic limit on the fraction of heat that can be converted to work, which affects combustion engines but not fuel cells.

Hydrogen-Oxygen Fuel Cell (Anodic half-equation)

The oxidation reaction at the anode in acidic conditions: $H_{2}(g) \rightarrow 2H^{+}(aq) + 2e^{-}$, with water as the only overall product.

Methanol Fuel Cell (Anodic half-equation)

The reaction at the anode where methanol is oxidized: $CH_{3}OH(aq) + H_{2}O(l) \rightarrow CO_{2}(g) + 6H^{+}(aq) + 6e^{-}$, producing $CO_{2}$ at the point of use.