6.1 Flashcards
What are alkanes?
A: Alkanes are a group of saturated hydrocarbons, meaning they contain only single carbon-carbon bonds.
What does the term “saturated” mean in the context of alkanes?
A: In the context of alkanes, “saturated” means that they contain only single carbon-carbon bonds; there are no double bonds present.
What is the general formula of alkanes?
A: The general formula of alkanes is CnH2n+2, where “n” represents the number of carbon atoms in the molecule.
: Describe the physical properties of alkanes.
A: Alkanes are generally colorless compounds with a gradual change in their physical properties as the number of carbon atoms in the chain increases.
Q: Are alkanes reactive compounds?
A: Generally, alkanes are unreactive compounds. However, they do undergo combustion reactions and can be cracked into smaller, more useful molecules.
Q: What is methane and its significance?
A: Methane is an alkane and is the major component of natural gas, making it important both as a fuel source and as a greenhouse gas.
Q: List the first five members of the alkane homologous series.
A: Methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), and pentane (C5H12).
Q: Explain the combustion reactions of alkanes.
A: Alkanes undergo combustion in the presence of air. Complete combustion results in the formation of water and carbon dioxide gas. For example, methane burns as follows: CH4 + 2O2 → CO2 + 2H2O.
Q: What is the composition of gasoline, and what happens during its combustion?
A: Gasoline is largely composed of isomers of octane (C8H18). During combustion, it requires large amounts of oxygen to combust fully, forming carbon dioxide and water. For example: 2C8H18 + 25O2 → 16CO2 + 18H2O.
What environmental problems are associated with the combustion of hydrocarbons?
A: Car exhaust contains small amounts of unburnt hydrocarbons, carbon monoxide, and soot, all of which contribute to environmental problems. Additionally, carbon dioxide, a product of combustion, is a major contributor to global warming.
Q: What are alkenes?
A: Alkenes are unsaturated hydrocarbons containing a double carbon-carbon bond (C=C
Q: How is the double carbon-carbon bond represented in alkenes?
A: The double carbon-carbon bond in alkenes is represented as two lines between two carbon atoms, denoted as C=C.
Q: What is the functional group in alkenes, and why is it important?
A: The functional group in alkenes is the double carbon-carbon bond (C=C). It is significant because it allows alkenes to react in ways that alkanes cannot, imparting unique chemical properties.
Can you provide examples of the first four alkenes in the homologous series?
A: The first four alkenes in the homologous series are ethene (C2H4), propene (C3H6), but-1-ene (C4H8), and pent-1-ene (C5H10).
Q: What does it mean for a compound to be unsaturated?
A: A compound is considered unsaturated if it contains one or more double or triple bonds between carbon atoms. In the context of alkenes, the presence of the C=C double bond makes them unsaturated.
How does the presence of a double bond affect the reactivity of alkenes compared to alkanes?
A: Alkenes are more reactive than alkanes due to the presence of the double bond. This double bond can be opened up, allowing incoming atoms to form additional single bonds with each carbon atom of the functional group.
Q: What happens when the double bond in alkenes is opened up?
A: Opening up the double bond in alkenes allows each carbon atom to form four single bonds instead of one double bond and two single bonds. This makes alkenes more reactive and capable of forming additional bonds with other atoms or molecules.
Q: What term is used to describe compounds with a C=C double bond?
A: Compounds containing a C=C double bond are referred to as unsaturated compounds due to their ability to form additional bonds with other atoms or molecules.
How do alkenes compare to alkanes in terms of reactivity?
A: Alkenes are generally more reactive than alkanes due to the presence of the double bond, which allows for a wider range of chemical reactions, including addition reactions. Alkanes, being saturated hydrocarbons, are relatively inert and undergo limited reactions compared to alkenes.
Q: What type of combustion do alkenes undergo, and why is incomplete combustion more common for alkenes?
A: Alkenes undergo both complete and incomplete combustion, but incomplete combustion is more common due to their higher carbon to hydrogen ratio. This results in a smoky flame in air.
Q: What happens during incomplete combustion of butene when there is insufficient oxygen?
A: Incomplete combustion of butene in insufficient oxygen produces a mixture of carbon monoxide and water: C4H8 + 4O2 → 4CO + 4H2O.
Q: How is soot produced during the combustion of alkenes?
A: Soot, consisting of carbon particles, is produced when alkenes undergo incomplete combustion in conditions of limited oxygen. For example: C4H8 + 2O2 → 4C + 4H2O.
What type of reaction do alkenes mainly undergo, and what allows them to react in this manner?
A: Alkenes mainly undergo addition reactions, facilitated by the presence of the C=C double bond functional group, which allows for the opening of the double bond and the addition of atoms across it.
Q: What is the process of hydrogenation, and what catalyst is used?
A: Hydrogenation is an addition reaction in which alkenes react with hydrogen to form alkanes. It occurs at 150ºC using a nickel catalyst.
Q: How is hydrogenation used in the food industry?
A: Hydrogenation is used in the food industry to manufacture margarine from vegetable oils. It involves partially hydrogenating polyunsaturated vegetable oils to increase their molecular weight and convert them into solid fats.
Q: Describe the process of halogenation with alkenes.
A: Halogenation involves halogens participating in addition reactions with alkenes, where the halogen atoms add across the C=C double bond. This reaction occurs readily at room temperature
Q: What is the bromine water test, and how does it differentiate between alkanes and alkenes?
A: The bromine water test is a chemical test used to differentiate between alkanes and alkenes. Bromine water, which is orange in color, will remain orange when added to an alkane but will lose its color when added to an alkene due to the addition of bromine across the C=C double bond.
Q: What are polymers, and how are they formed?
A: Polymers are large molecules with high relative molecular mass, formed by linking together numerous smaller molecules known as monomers. Each monomer serves as a repeat unit and is connected to adjacent units via covalent bonds.
Q: What is the role of polymerisation reactions in the formation of polymers?
A: Polymerisation reactions involve the linking of monomers to form polymers. These reactions typically require high pressures and often involve the use of catalysts to facilitate the bonding of monomers into long polymer chains.
Q: Give examples of everyday materials that are polymers.
A: Many everyday materials, such as resins, plastics, polystyrene cups, and nylon, are examples of polymers. These are often manufactured and are known as synthetic polymers.
Q: How do synthetic polymers differ from natural or biological polymers?
A: Synthetic polymers are manufactured by humans through industrial processes, while natural or biological polymers are produced by living organisms or found in nature. Examples of natural polymers include proteins, cellulose, and DNA
Q: How are addition polymers formed, and what type of monomers are involved?
A: Addition polymers are formed by the joining of many monomers, typically those containing carbon-carbon double (C=C) bonds. During polymerization, one of the bonds in each C=C bond breaks, and a bond is formed with the adjacent monomer, resulting in a polymer with only single bonds.
Q: What are some examples of monomers used in the formation of addition polymers?
A: Addition polymers can be made from various alkene monomers, including ethene, propene, and others. Additionally, some polymers are formed from alkene monomers with different atoms attached, such as chlorine or hydroxyl groups.
Q: How are addition polymers named?
A: The name of an addition polymer is determined by placing the name of the monomer in brackets and adding “poly-“ as the prefix. For example, if propene is the alkene monomer used, the polymer is named polypropene. Similarly, polyethene is formed by the addition polymerization of ethene monomers.
Q: How can you deduce the monomer from the polymer structure?
A: To deduce the monomer from the polymer structure, you can reverse the process of polymerization. Start by identifying the repeat unit within the polymer structure, which involves changing the double bond in the monomer to a single bond in the repeat unit and adding bonds to each end of the repeat unit to indicate continuation. Then, add the rest of the groups in the same order they surrounded the double bond in the monomer. Finally, add a subscript “n” to indicate a large number of repeat units.
Q: How are condensation polymers formed, and what distinguishes them from addition polymers?
A: Condensation polymers are formed when two different monomers are linked together with the removal of a small molecule, typically water. This removal of a small molecule distinguishes condensation polymers from addition polymers, where no small molecule is eliminated during polymerization
Q: What types of functional groups do monomers in condensation polymers typically have, and how do they react during polymerization?
A: The monomers in condensation polymers typically have two functional groups present, one on each end. Examples include diols (alcohol at each end) or dicarboxylic acids (carboxylic acid at each end). During polymerization, the functional groups at the ends of one monomer react with the functional group on the end of the other monomer, resulting in the formation of long chains with an A-B-A-B pattern
Q: What is the significance of the A-B-A-B pattern in condensation polymers?
A: The A-B-A-B pattern in condensation polymers arises from the alternating arrangement of monomers along the polymer chain. This pattern reflects the repeating sequence of functional groups from the monomers and contributes to the overall structure and properties of the polymer.
Q: Can monomers with different functional groups react to form condensation polymers?
A: Yes, monomers with different functional groups can react to form condensation polymers. For example, polyesters are often formed from two different monomers, such as diols and dicarboxylic acids, resulting in the elimination of water during polymerization
Q: What are the two main types of synthetic condensation polymers, and how do they differ?
A: The two main types of synthetic condensation polymers are polyesters and polyamides. Polyesters are formed from diols and dicarboxylic acids, while polyamides are formed from diamines and dicarboxylic acids. These polymers differ in their chemical composition and properties.
Q: How are polyesters formed, and what are the typical monomers involved in their synthesis?
A: Polyesters are formed from dicarboxylic acid monomers (containing a carboxylic acid group, -COOH, at each end) and diols (containing an alcohol group, -OH, at each end). During polymerization, each -COOH group reacts with the -OH group on a diol from another monomer, forming an ester link (-COO-) and releasing one water molecule per linkage.
Q: What is the chemical process involved in forming ester links during polyester synthesis?
A: The formation of ester links during polyester synthesis involves a condensation reaction, where the -COOH group of a dicarboxylic acid reacts with the -OH group of a diol. This reaction results in the loss of one water molecule (H2O), formed from the combination of a hydrogen ion (H+) from the -COOH group and a hydroxide ion (OH-) from the -OH group.
Q: Can you provide an example of a polyester, and what are some of its properties or applications?
A: Terylene is an example of a polyester. It is a synthetic polymer known for its durability, wrinkle resistance, and resistance to stretching and shrinking. Terylene is commonly used in clothing, upholstery, and packaging materials due to its excellent mechanical properties and resistance to environmental factors such as moisture and sunlight.
Question: What are the health and safety aspects to consider when working with the solutions used in the formation of condensation polymers?
Answer:
Solutions used are hazardous and contain toxic materials and solvents.
Handle and dispose of them with care.
Use small quantities to minimize risks.
Question: Describe the procedure for making nylon in the lab.
Answer:
Prepare two solutions: one containing 1,6-diaminohexane in water, and the other containing decanedioyl dichloride in cyclohexane.
Pour 5 cm³ of aqueous 1,6-diaminohexane solution into a 25 cm³ beaker.
Carefully add 5 cm³ of decanedioyl dichloride solution on top to minimize mixing.
The dichloride solution floats on top without mixing, and a white nylon film forms at the interface.
Pick up a little of the film with tweezers and wrap it around a glass rod.
Rotate the glass rod to extract a “rope” of nylon from the beaker.
Question: What is the principle behind the formation of nylon in the lab?
Nylon formation involves two monomers, each containing reactive groups at their ends.
These groups react, joining together to form long chains, akin to a bead necklace with alternating colored beads.
The resulting nylon is named after New York and London, where it was first discovered.
Question: What is the significance of the term “nylon 6,10” in the context of nylon formation?
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Answer:
“Nylon 6,10” indicates the lengths of the monomer pieces: 6 carbons long from the diamine and 10 carbons long from the diacyl chloride.
It refers to the specific composition of the monomers used in the polymerization process
Question: How does the nylon rope trick demonstrate the polymerization process?
Answer:
The nylon rope trick showcases the formation of long chains of nylon from the reaction of two monomers.
By rotating the glass rod, a continuous “rope” of nylon is extracted, demonstrating the polymerization process visually.
Question: What is DNA, and what is its primary function?
Answer:
DNA stands for Deoxyribonucleic acid and is a large molecule essential to all life.
Its primary function is to store genetic information and encode instructions necessary for the development and functioning of organisms.
Question: Describe the composition of DNA.
Answer:
DNA consists of nucleotides, which are made up of three components: a phosphate group, a sugar molecule (deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine)
Question: What are the four different bases in DNA, and how are they abbreviated?
Answer:
The four bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
Question: Explain the structure of DNA.
Answer:
DNA consists of two strands that intertwine to form a double helix.
The strands are held together by hydrogen bonds between complementary base pairs: A with T, and C with
Question: How is genetic information stored in DNA?
Answer:
Genetic information is stored in the sequence of the bases along the DNA strands.
The order of the bases serves as a code for the organism’s genes, determining its traits and functions.
Question: What is the significance of the double helix structure of DNA?
Answer:
The double helix structure of DNA provides stability and protection for the genetic information stored within.
It allows for the efficient packaging of DNA within cells and facilitates processes such as replication and transcription
