Questions and Answers
What is the product formed when ethene reacts with bromine?
Which catalyst is used when ethene is hydrated to form ethanol?
What process is used to convert vegetable oils into solid fats?
What is a common use of alkenes in industry?
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During the addition reaction of ethene with hydrogen, what alkane is produced?
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What distinguishes each member of the homologous series of alkanes from the next?
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Which of the following best describes the general reactivity of alkanes?
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What products are formed when alkanes combust in the presence of oxygen?
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What is the outcome when alkanes react with halogens under UV light?
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Which alkane has the molecular formula C4H10?
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Study Notes
Hydrocarbons Overview
- Homologous series of alkanes differ by -CH2 in molecular formula.
- Key alkanes and their properties include:
- Methane (CH4): 1 carbon, molecular mass 16, boiling point -162°C
- Ethane (C2H6): 2 carbons, molecular mass 30, boiling point -89°C
- Propane (C3H8): 3 carbons, molecular mass 44, boiling point -42°C
- Butane (C4H10): 4 carbons, molecular mass 58, boiling point -0.5°C
- Pentane (C5H12): 5 carbons, molecular mass 72, boiling point 36°C
Structure of Alkanes
- Alkanes consist of covalent molecules with each carbon atom bonded to four other atoms via single covalent bonds.
- Common structural formulas include:
- Methane: CH4
- Ethane: C2H6
- Propane: C3H8
- Butane: C4H10
- Pentane: C5H12
Chemical Properties of Alkanes
- Alkanes are largely unreactive due to saturated carbon-carbon bonds.
- They undergo combustion to produce carbon dioxide and water vapor:
- Example: CH4 + 2O2 → CO2 + 2H2O
- React with halogens (e.g., chlorine) under UV light or heat, resulting in halogenoalkanes:
- Example: C2H4 + Br2 → C2H4Br2
Chemical Properties of Alkenes
- Alkenes undergo addition reactions:
- Hydration: Ethene reacts with steam to form ethanol using phosphoric acid at 300°C:
- C2H4 + H2O → C2H5OH
- Hydrogenation: Ethene reacts with hydrogen in presence of nickel to form ethane:
- C2H4 + H2 → C2H6
- Hydration: Ethene reacts with steam to form ethanol using phosphoric acid at 300°C:
- These reactions are industrially significant for the production of ethanol and converting vegetable oils into solid fats.
Uses of Alkenes
- Versatile starting materials for chemicals and plastics (e.g., poly(ethene), PVC, Teflon).
- Lower alkenes can be obtained from kerosene or petrol and used as fuel.
Uses of Alkanes and Their Derivatives
- Positive aspects:
- Alkanes serve as fuels due to high exothermic combustion.
- Natural gas (primarily methane) is widely used in power stations and vehicles.
- Liquefied petroleum gas (LPG) is common for cooking and automotive applications.
- Substituted alkanes (e.g., CFCs) are utilized in refrigeration, propellants, and solvents.
- Negative aspects:
- CFCs contribute significantly to ozone layer depletion through chlorine free radicals.
- Efforts are being made to replace CFCs with environmentally friendly alternatives.
Quick Checks and Solutions
- Isomers of pentane share the same molecular formula (C5H12) but have different structural arrangements.
- Chemical formulas for alkanes:
- Eight carbon atoms: C8H18
- Twenty carbon atoms: C20H42
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Description
Test your knowledge on the homologous series of alkanes, including their chemical names, molecular formulas, molecular masses, and boiling points. This quiz covers the basic properties and relationships within the alkane family, helping you understand the incremental changes as carbon atoms increase. Perfect for chemistry students looking to reinforce their learning.
