Hydrocarbons Practice Questions
17 free Hydrocarbons practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What are hydrocarbons primarily composed of?
- A Carbon and hydrogen
- B Carbon and oxygen
- C Hydrogen and nitrogen
- D Carbon and sulfur
Correct answer: Carbon and hydrogen
Hydrocarbons are organic compounds consisting only of carbon and hydrogen atoms. They form the basic framework of many organic molecules and fuels.
Which hydrocarbon contains a carbon-carbon double bond?
- A Alkane
- B Alkene
- C Alkyne
- D Arene
Correct answer: Alkene
Alkenes contain at least one carbon-carbon double bond. These compounds are unsaturated and generally more reactive than alkanes.
Which hydrocarbon contains a carbon-carbon triple bond?
- A Alkane
- B Alkene
- C Alkyne
- D Cycloalkane
Correct answer: Alkyne
Alkynes are hydrocarbons with at least one carbon-carbon triple bond. This bond makes them highly reactive compared to alkanes.
Which is the simplest alkane?
- A Ethane
- B Methane
- C Propane
- D Butane
Correct answer: Methane
Methane (CH4) is the simplest alkane with one carbon atom bonded to four hydrogen atoms. It is the main component of natural gas.
What is the general formula for alkenes?
- A CnH2n+2
- B CnH2n
- C CnH2n−2
- D CnHn
Correct answer: CnH2n
Alkenes have the general formula CnH2n because they contain one double bond. This reduces the number of hydrogen atoms compared to alkanes.
Which hydrocarbon is used in welding due to its high flame temperature?
- A Methane
- B Propane
- C Ethyne
- D Ethene
Correct answer: Ethyne
Ethyne, better known as acetylene, burns with oxygen at around 3300 degrees Celsius, far hotter than methane, propane or ethene. That flame temperature is what makes the oxy-acetylene torch able to cut and weld steel.
Which type of hydrocarbons contains benzene rings?
- A Saturated alkanes
- B Alicyclic hydrocarbons
- C Unsaturated alkenes
- D Aromatic hydrocarbons
Correct answer: Aromatic hydrocarbons
Aromatic hydrocarbons are built around one or more benzene rings, in which six carbon atoms share a delocalised ring of electrons. Alicyclic hydrocarbons are also ring-shaped but have no such delocalised system, and alkanes and alkenes are open-chain.
Which type of reaction is characteristic of alkenes?
- A Substitution reaction
- B Elimination reaction
- C Redox reaction
- D Addition reaction
Correct answer: Addition reaction
The carbon-carbon double bond in an alkene is electron-rich, so reagents add across it and the double bond becomes a single bond in one saturated product. Substitution is characteristic of alkanes and arenes, while elimination is the route by which alkenes are usually formed rather than consumed.
Which hydrocarbon is used as a starting material in the production of plastics?
- A Ethene
- B Methane
- C Propane
- D Butane
Correct answer: Ethene
Ethene is widely used to produce polyethylene, a common plastic. The double bond allows polymerization reactions to occur.
Which hydrocarbon is the simplest member of the alkene series?
- A Ethene
- B Methane
- C Propene
- D Butene
Correct answer: Ethene
Ethene (C2H4) is the smallest alkene, with a double bond between its two carbon atoms. Methane contains no double bond at all, and propene and butene are larger members of the same series.
Which property is common to most hydrocarbons?
- A Highly soluble in water
- B Strongly acidic
- C Strongly basic
- D Insoluble in water
Correct answer: Insoluble in water
Hydrocarbons are generally nonpolar molecules. Because water is polar, hydrocarbons are typically insoluble in water.
What is the molecular formula of benzene?
- A C6H6
- B C2H4
- C C3H8
- D CH4
Correct answer: C6H6
Benzene has the molecular formula C6H6 and contains a ring of six carbon atoms with alternating double bonds. It is the simplest aromatic hydrocarbon.
Which type of hydrocarbon contains only single bonds and is fully saturated with hydrogen?
- A Alkene
- B Alkyne
- C Alkane
- D Aromatic hydrocarbon
Correct answer: Alkane
Alkanes are saturated hydrocarbons because all carbon atoms are connected by single bonds. They contain the maximum number of hydrogen atoms.
Which hydrocarbon series includes compounds with the general formula CnH2n−2?
- A Alkanes
- B Alkenes
- C Alkynes
- D Cycloalkanes
Correct answer: Alkynes
Alkynes follow the general formula CnH2n−2 due to the presence of a triple bond. This reduces the number of hydrogen atoms compared to alkanes and alkenes.
What is the primary source of most hydrocarbons used as fuels?
- A Petroleum
- B Seawater
- C Atmosphere
- D Volcanic gases
Correct answer: Petroleum
Petroleum and natural gas are the primary natural sources of hydrocarbons. They are processed to produce fuels such as gasoline, diesel, and LPG.
Which hydrocarbon is commonly used as a refrigerant and aerosol propellant?
- A Methane
- B Ethene
- C Ethyne
- D Propane
Correct answer: Propane
Propane is used in refrigeration systems and aerosol propellants because of its physical properties. It is also widely used as a fuel.
Which process breaks large hydrocarbon molecules into smaller ones in petroleum refining?
- A Distillation
- B Blending
- C Polymerization
- D Cracking
Correct answer: Cracking
Cracking uses heat or a catalyst to break long-chain hydrocarbons from crude oil into shorter, more useful molecules such as petrol and ethene. Distillation only separates the fractions already present in the crude oil, and blending simply mixes finished fractions together.