Bài 21: Alkane - Khái niệm và Phản ứng Đốt cháy

Which statement best defines a hydrocarbon?

• A compound containing only carbon and hydrogen

• A compound containing carbon, oxygen, and hydrogen

• A compound containing carbon and nitrogen only

• A compound containing metals and carbon atoms

Which description correctly identifies an alkane?

• A hydrocarbon with only single C–C bonds

• A hydrocarbon with at least one C=C bond

• A hydrocarbon with at least one C≡C bond

• A molecule with carbon, hydrogen, and oxygen

Which structural feature is common to methane, ethane, propane, and butane?

• Only single bonds between carbon atoms

• Alternating double and single bonds

• A triple bond at the chain end

• A ring of four carbon atoms

During complete combustion of butane (C4H10), which products form?

• Carbon dioxide and water only

• Carbon monoxide and water only

• Carbon dioxide and hydrogen only

• Soot and water only

A lighter uses butane as fuel. The flame becomes yellow and sooty when oxygen is limited. Which change best restores clean blue combustion?

• Increase air supply to the flame

• Decrease the fuel flow rate only

• Cool the flame with water vapor

• Use methane instead of butane

Which statement best explains why alkanes such as methane, propane, and butane are widely used as fuels in daily life?

• They burn cleanly with high energy per mole

• They dissolve easily in water for storage

• They react quickly with bromine at room temperature

• They are unsaturated and polymerize during use

Ethylene (ethene) is the simplest alkene. Which condensed structural formula represents ethylene?

• CH2=CH2 with one double bond

• CH3–CH3 with only single bonds

• CH≡CH with a triple bond

• CH3–CH2–CH3 with three carbons

Which description correctly identifies a general feature of alkenes?

• Hydrocarbons containing at least one C=C bond

• Hydrocarbons containing only single C–C bonds

• Hydrocarbons containing at least one C≡C bond

• Hydrocarbons with oxygen-containing functional groups

A student compares burning methane and propane under the same conditions. Which claim uses evidence to justify a difference in heat released?

• Propane releases more heat per mole than methane

• Methane releases more heat per mole than propane

• Both release the same heat per mole always

• Heat release depends only on burner shape

Which set of properties best matches ethylene at room conditions?

• Colorless, odorless gas, sparingly soluble in water

• Colored, pungent liquid, highly soluble in water

• Colorless, sweet-smelling solid, dense in water

• Brown, strong odor gas, instantly bleaches bromine