Chemistry - organic

Hydrocarbon

Compounds composed of only carbon and hydrogen

homologous seires

A sequence of compounds with the same functional group and similar chemical properties

Molecular formula for alkanes

CnH2n+2

Molecular formula for alkenes

CnH2n

Molecular formula for alcohols

CnH2n+1OH

Molecular formula for carboxylic acid

CnH2n+1COOH (where n is the number of carbon atoms in the molecule, minus 1)

How bromine water and magnesium or carbonate can distinguish between molecules

Bromine water can distinguish between molecules based on the presence of double or triple bonds (alkenes and alkynes) and the presence of carbonate or bicarbonate ions. Alkenes and alkynes will decolorize bromine water, while alkanes will not. Magnesium or carbonate can distinguish between carbonate and bicarbonate ions based on the formation of a white precipitate and the release of carbon dioxide gas.

Observations of carboxylic acid reacting with metals and carbonates

When carboxylic acids react with metals, observations include the formation of a salt and the release of hydrogen gas, often as effervescence (fizzing).Reaction with carbonates produces a salt, water, and carbon dioxide, which is also indicated by effervescence.

Observations of alkanes and alkenes reacting to bromine water

When alkanes and alkenes react with bromine water, alkanes show no reaction this is because alkanes have single carbon-carbon bonds (C-C) and do not have double bonds (C=C) to react with bromine and need uv light. While alkenes react to decolourize the bromine water rapidly. The bromine atoms add across the double carbon-carbon bond (C=C) in the alkene, forming an addition product. This addition reaction removes the bromine from the solution, causing the colour change. Alkenes are more reactive than alkanes due to the presence of the double bond, which has a higher electron density.Bromine water is an orange-brown solution that becomes colorless when mixed with an alkene, indicating an addition reaction has occurred.

Word equation for bromine water and metals

Metal + bromine water = metal oxide + hydrogen
E.g.
Ethylene + Bromine --> 1,2-Dibromoethane + hydrogen gas
(brownish-red) (colorless)

CASH2OCO2

carbonate + acid -> salt + water + carbon dioxide

State the trend in melting and boiling points for straight chain molecules

For straight-chain molecules, both melting and boiling points generally increase as the number of carbon atoms in the chain increases This is because longer chains lead to stronger intermolecular forces, which require more energy to overcome. Stronger intermolecular forces mean that more energy is required to break those forces and separate the molecules into a liquid (melting) or gas (boiling) phase.

Determine the state at room temperature of various organic molecules given their melting and boiling point

You need to compare its melting and boiling points with this temperature. If the melting point is below room temperature and the boiling point is above room temperature, the molecule is a liquid.If the melting point is above room temperature, it's a solid.If the boiling point is below room temperature, it's a gas.

Explain the solubility of alkanes, alkenes, alcohols, and carboxylic acids in water with reference to forces of attraction between those molecules and water.

Alkanes and alkenes are virtually insoluble in water due to a mismatch in intermolecular forces. Water molecules are strongly attracted to each other through hydrogen bonds, These weak forces are not strong enough to disrupt the hydrogen bonds in water, preventing alkanes from dissolving. Alcohols' solubility in water stems from their ability to form hydrogen bonds with water molecules. The hydroxyl group (-OH) in alcohols, which is hydrophilic, readily interacts with water's polar nature, leading to strong hydrogen bonds. These hydrogen bonds help dissolve the alcohol molecules in water, making alcohols generally soluble, especially those with shorter carbon chains. Carboxylic acids with shorter carbon chains (1-4 carbons) are soluble in water due to strong hydrogen bonding between the carboxyl group of the acid and water molecules. Longer chain carboxylic acids become less soluble as the hydrophobic, nonpolar hydrocarbon chain interferes with water's hydrogen bonding network.

Define crude oil and explain how fractional distillation is used to separate it into hydrocarbons using differences in boiling point.

Crude oil, a naturally occurring mixture, is composed of various hydrocarbons with different chain lengths and boiling points. Fractional distillation separates these hydrocarbons by exploiting these differences, using a tall, temperature-gradient column to condense them into fractions based on their boiling points.

Things at the top layer of fractional distillation

At the top of a fractional distillation tower, you'll find the lightest and most volatile components, including petroleum gases like propane and butane. These gases have short carbon chains and low boiling points, causing them to vaporize and rise to the top of the tower where it's cooler. The top of the tower is also where the condensed vapors are collected and further processed

Things at the bottom layer of fractional distillation

At the bottom layer of a fractional distillation column, you'll find the heaviest, most viscous fractions, such as bitumen and heavy gas oil, which are also called residuals. These are the hydrocarbons with the longest carbon chains and highest boiling points, and they condense at the bottom because of the higher temperature there.

Fractional distillation

separation of crude oil into fractions differing in boiling point (and hence chemical composition) by means of distillation, typically using a fractionating column.

Describe the requirements of complete and incomplete combustion

Complete combustion has a plentiful supply of oxygen, leading to the formation of carbon dioxide (CO2) and water (H2O). Incomplete combustion, on the other hand, occurs when oxygen is limited, resulting in the production of carbon monoxide (CO) and/or carbon particles, along with water.

Write word equations for incomplete combustion

Gas + Oxygen → Carbon + Water + Carbon Monoxide

Write word equations for complete combustion

fuel + oxygen → carbon dioxide + water.

Define a monomer and a polymer, and explain the difference in their properties

A monomer is a small molecule that can chemically bond with other similar molecules to form a larger molecule called a polymer. Polymers are essentially long chains of repeating monomers. The key difference lies in size and complexity: monomers are single units, while polymers are large, repeating structures.

Explain the process of polymerization

Polymerization is a chemical process where many small monomer molecules combine to form a large, long-chain molecule called a polymer. High temperature, High pressure and a catalyst are necessary to speed up the reaction (catalyst), and supply the energy to break the C=C and for C-C single bonds between the molecules (high temperature/high pressure)

Identify a common polymer and its uses

A very common polymer is polyethylene (PE), and it's used extensively for packaging, bottles, and various other plastic items. Specifically, low-density polyethylene (LDPE) is used in bags and containers, while high-density polyethylene (HDPE) is used in bottles and crates.

Relate the properties of a polymer to its uses

A polymer's properties, like flexibility, strength, and chemical resistance, directly dictate its suitability for various applications. For example, strong, durable polymers are used in construction, while flexible polymers are ideal for packaging or clothing. Specific properties, like heat resistance or biocompatibility, are crucial for specialized uses in medical devices or high-temperature applications.

Suffix of alkanes

-ane

Suffix of alkenes

-ene

Suffix of alcohol

-ol

Suffix of carboxylic acid

-oic acid