National 5 Chemistry Unit 2 - Nature's Chemistry

A set of flashcards covering the key information for Unit 2 from the National 5 Chemistry course specification, with some miscellaneous practice questions peppered in.

What is a homologous series?

A family of compounds with the same general formula and similar chemical properties.

What is the definition of a hydrocarbon?

A compound containing hydrogen and carbon atoms only.

What is the general formula for the alkanes?

CnH2n+2

Give one use of alkanes.

Fuels

What is the general formula for the cycloalkanes?

CnH2n

Give two uses for cycloalkanes.

Cycloakanes are used as fuels and solvents.

What is the general formula for the alkenes?

CnH2n

Give two uses of alkenes.

Alkenes are used to make polymers and alcohols.

What does it mean if a hydrocarbon is saturated?

There are only single carbon to carbon bonds.

What does is mean if a hydrocarbon is unsaturated?

There is at least one double carbon to carbon bond.

What is the test for saturation?

Reaction with bromine solution; if the bromine solution decolourises, then the compound is unsaturated.

Are alkanes saturated or unsaturated?

They are saturated as they have only single carbon to carbon bonds.

Are alkenes saturated or unsaturated?

They are unsaturated because they always have at least one double carbon to carbon bond.

Why are cycloalkanes easy to identify by looking at their full structural formula?

Because their carbons are arranged in a ring.

What is the first member of the alkane homologous series?

Methane/CH4.

What is the first member of the alkene homologous series?

Ethene/C2H4. Methene cannot exist because there is only one carbon and so there could not be a double carbon to carbon bond.

In a homologous series, as the molecular size increases, what happens to the melting and boiling points?

The melting and boiling points increase.

Why do the melting and boiling points increase as the molecular size increases?

This is due to the increasing strength of the intermolecular forces.

What is the definition of an isomer?

An isomer is a compound with the same molecular formula but a different structural formula.

Name the three types of addition reaction that alkenes can undergo.

Halogenation, hydration, and hydrogenation.

What is halogenation?

Halogenation is an addition reaction in which a halogen is added across an alkene's double bond, forming a dihaloalkane.

What is hydration?

Hydration is an addition reaction in which water (H2O) is added across an alkene's double bond, forming an alcohol.

What is hydrogenation?

Hydrogenation is an addition reaction in which hydrogen (H2) is added across an alkene's double bond, forming the corresponding alkane.

Hydrogen reacts with ethene in an addition reaction. State what the product of the reaction would be.

Ethane

What is the name given to reactions that involve the addition of HBr?

Halogenation, as both hydrogen (H) and bromine (Br) are halogens.

Give two uses of alcohols.

Fuels and solvents

Why are alcohols good fuels?

They are highly flammable and burn with very clean flames.

What is the functional group found in alcohols?

The hydroxyl group -OH

Give the general formula for the alcohols.

CnH2n+1OH

What is the first member of the alcohols homologous series?

Methanol

Methanol, ethanol, and propanol are miscible with water. What does miscible mean?

They mix freely with water to form a solution.

As the molecular size of the alcohols increases, what happens to their solubility?

The solubility decreases.

Give three uses of carboxylic acids.

Soaps, medicines, and preservatives.

What is the functional group found in carboxylic acids?

The carboxyl group -COOH

Give the general formula for the carboxylic acids.

CnH2n+1COOH

Which carboxylic acid is found in vinegar?

Ethanoic acid

Draw the full structural formula for butanoic acid.

(see image)

What is combustion?

Combustion is when a fuel burns in oxygen, releasing energy.

Give the word equation for the complete combustion of a hydrocarbon.

hydrocarbon + oxygen ---> carbon dioxide + water

Give the balanced chemical equation for the complete combustion of methane.

CH4 + 2O2 ---> CO2 + 2H2O

What is the formula used to calculate the quantity of heat energy released?

Eh = cmΔT

What is meant by the term exothermic?

A reaction in which heat energy is given out (surroundings get hotter).

What is meant by the term endothermic?

A reaction in which heat energy is taken in (surroundings get colder).