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It is essential for students to study from this file.

Definition:
- Alkanes are saturated hydrocarbons comprised solely of single C-C and C-H bonds.
General Formula:
- The general formula for alkanes is represented as $CnH{2n+2}$ .

Alkanes are non-polar molecules.
Their boiling points exhibit an increase in line with the chain length, which is attributed to stronger Van der Waals forces.
When branching occurs within the molecular structure, the boiling point is lowered; this is due to the fact that branched molecules cannot pack as closely together compared to straight-chain alkanes.

Fractional distillation is a method utilized to separate crude oil into its component fractions based on varying boiling points.

Purpose of Cracking:
- Used for breaking down large, low-demand alkanes into more useful smaller alkanes (fuels) and alkenes (for polymer production).
Thermal Cracking:
- Involves high temperature and pressure, producing numerous alkenes.
Catalytic Cracking:
- Conducted at lower temperature and slight pressure, utilizing a zeolite catalyst; leads to the production of branched alkanes and benzene rings.

Complete Combustion:
- Results in the formation of carbon dioxide (CO2) and water (H2O).
Incomplete Combustion:
- Yields carbon monoxide (CO), which is toxic, or soot (C).
Internal Combustion Engines:
- Release nitrogen oxides (NOx) from the reactions of nitrogen and oxygen in the air at elevated temperatures, and sulfur dioxide (SO2) resulting from sulfur impurities in the fuel.
Catalytic Converters:
- Function to convert pollutants in exhaust gases; the reaction can be expressed as:
- $2CO + 2NO ightarrow 2CO2 + N2$ .

Structure:
- Halogenoalkanes are alkanes in which one or more hydrogen atoms have been substituted with a halogen (F, Cl, Br, I).
General Formula:
- The general formula can be expressed as $CnH{2n+1}X$ where X is the halogen.

The carbon-halogen (C-X) bond is characterized by polarity due to the higher electronegativity of halogens compared to carbon.
This results in a partial positive charge (δ+) on the carbon atom, making it more prone to nucleophilic attack.

The reactivity of halogenoalkanes is influenced by bond enthalpy; specifically, the C-I bond is the weakest and therefore breaks most readily. Thus, iodoalkanes are more reactive compared to chloroalkanes, even though they are less polar.

Nucleophilic Substitution:
- This reaction type involves a nucleophile displacing the halogen in a halogenoalkane.
Nucleophiles:
- Defined as molecules possessing a lone pair of electrons; examples include hydroxide ions (OH), cyanide ions (CN), and ammonia (NH3).
Mechanism:
- Illustrated using curly arrows, which denote the movement of electron pairs.
Elimination Reactions:
- Under certain conditions (e.g., use of ethanol as a solvent and elevated temperatures), hydroxide ions can act as a base, leading to the removal of both a hydrogen ion and a halide ion from a halogenoalkane, resulting in the formation of an alkene.

Reaction Type	Reagent/Condition	Role of OH-	Product
Substitution	Aqueous KOH, warm	Nucleophile	Alcohol
Elimination	Ethanolic KOH, hot	Base	Alkene

Which type of isomerism occurs when the functional group is attached to a different carbon atom in the same chain?
- a) Chain isomerism
- b) Position isomerism
- c) Functional group isomerism
- d) Stereoisomerism
Which catalyst is used in the catalytic cracking of long-chain alkanes?
- a) Iron
- b) Platinum
- c) Zeolite
- d) Nickel
What is the primary role of a catalytic converter in a car?
- a) To increase fuel efficiency
- b) To convert CO and NO into CO2 and N2
- c) To remove sulfur from petrol
- d) To speed up the combustion of octane
Which bond is the most reactive in a halogenoalkane?
- a) C-F
- b) C-Cl
- c) C-Br
- d) C-I
What does a "curly arrow" represent in a reaction mechanism?
- a) The movement of an atom
- b) The vibration of a bond
- c) The movement of a pair of electrons
- d) The direction of the reaction

State whether the following statements are True or False (5 questions, 14 marks).

Branching in an alkane chain increases the boiling point.
Thermal cracking produces a high proportion of alkenes.
In a nucleophilic substitution reaction, the OH-ion acts as an electron pair donor.
Flue gas desulfurization uses calcium oxide to remove SO₂ from power station emissions.
The C-X bond in halogenoalkanes is non-polar.

Use the terms in the box below to fill the blanks (42 marks).
Box: [Nucleophile, Elimination, Substitution, Electronegativity, Enthalpy, Saturated, Fractional, Isomer]

Alkanes are known as saturated hydrocarbons because they contain no double bonds.
Crude oil is separated into simpler mixtures using fractional distillation.
A molecule with a lone pair of electrons that attacks a 8+ carbon is called a nucleophile.
The reactivity of halogenoalkanes is determined more by bond enthalpy than by bond polarity.
In an elimination reaction, a halogenoalkane loses a hydrogen halide to form an alkene.
The standard naming system for organic molecules is governed by the IUPAC.

Mechanism Drawing (15 Marks):
- Draw the mechanism for the nucleophilic substitution of 1-bromopropane with aqueous hydroxide ions (OH).
- Use curly arrows to demonstrate the movement of electrons and specify the partial charges (δ+ and δ-).
Comparative Analysis (15 Marks):
- A student reacts 2-bromopropane with KOH under two different conditions:
  - Condition A: Warm and Aqueous.
  - Condition B: Hot and Ethanolic.
- Name the organic product produced in each condition and specify the role of the OH-ion in each case (either Nucleophile or Base).