IGCSE Alkanes and Alkenes

What is the general formula for alkanes?

• C(n-1)H(2n-1)

• CnH(2n+2)

• C2nH2n

• CnH2n

Name the first three alkanes in the homologous series.

• Acetylene, Benzene, Toluene

• Methanol, Ethanol, Propanol

• Methane, Ethane, Propane

• Butane, Pentane, Hexane

What type of reaction occurs when alkenes react with hydrogen?

• Hydrolysis

• Oxidation

• Dehydrogenation

• Hydrogenation

Describe the process of cracking in the context of hydrocarbons.

• Cracking refers to the solidification of hydrocarbons at low temperatures.

• Cracking is the method of purifying hydrocarbons by distillation.

• Cracking is the process of combining small hydrocarbons into larger molecules.

• Cracking is the process of breaking down large hydrocarbon molecules into smaller, more useful hydrocarbons.

What is the main difference between alkanes and alkenes?

• The main difference is that alkanes have only single bonds, whereas alkenes have at least one double bond.

• Alkenes have a higher molecular weight than alkanes.

• Alkanes are more reactive than alkenes due to their structure.

• Alkanes contain double bonds, while alkenes contain only single bonds.

How do you test for the presence of alkenes?

• Heat the sample; a change in temperature indicates the presence of alkenes.

• Add water; a color change to blue indicates the presence of alkenes.

• Add bromine water; a color change from brown to colorless indicates the presence of alkenes.

• Add vinegar; a fizz indicates the presence of alkenes.

What is the general formula for alkenes?

• CnH2n+1

• CnH2n

• CnH2n-2

• CnH2n-1

Explain what is meant by a substitution reaction in alkanes.

• A substitution reaction in alkanes is a chemical reaction where one atom or group in the alkane is replaced by another atom or group.

• A substitution reaction in alkanes is a process where two alkanes combine to form a larger alkane.

• A substitution reaction in alkanes involves the addition of new atoms without replacing any existing ones.

• A substitution reaction in alkanes is when an alkane decomposes into smaller molecules.

What are the products of the complete combustion of alkanes?

• Methane (CH4) and ethane (C2H6)

• Carbon dioxide (CO2) and water (H2O)

• Carbon monoxide (CO) and hydrogen (H2)

• Oxygen (O2) and nitrogen (N2)

How does fractional distillation separate components of crude oil?

• Fractional distillation separates crude oil into different components based on their boiling points.

• Fractional distillation combines crude oil into a single product.

• Fractional distillation relies on the density of crude oil components.

• Fractional distillation uses chemical reactions to separate crude oil.