National 5 Chemistry : Unit 2 Nature's Chemistry

Comprehensive practice flashcards covering homologous series (alkanes, alkenes, cycloalkanes), consumer products (alcohols, carboxylic acids), isomerism, and energy calculations from fuel combustion.

What is a hydrocarbon?

A molecule that contains the elements carbon and hydrogen.

What is a homologous series?

Homologous series are a group of compounds that have same general formula, similar chemical properties and gradual change in physical properties.

What is the general formula for Alkanes ?

$$C_nH_{2n+2}$$

What is the general formula for Alkenes ?

$$C_nH_{2n}$$

What is the general formula for Cycloalkanes ?

$$C_nH_{2n}$$

What are saturated hydrocarbons ?

Hydrocarbons that have a single carbon to carbon bonds

What are unsaturated hydrocarbons ?

Hydrocarbons that have double carbon to carbon bonds

Why do the melting and boiling points increase as you descend a homologous series?

As molecular size increases, the strength of the intermolecular forces between molecules increases

How can bromine solution be used to distinguish between a saturated and an unsaturated hydrocarbon?

Unsaturated hydrocarbons (alkenes) quickly decolourise red/orange bromine solution by addition reaction, whereas saturated hydrocarbons (alkanes and cycloalkanes) decolourise it very slowly.

What is hydrogenation ?

Is an addition reaction in which hydrogen is added to an unsaturated compound such as an alkene

What is halogenation ?

Is an addition reaction in which halogen is added to an unsaturated compound such as an alkene

What is hydration ?

Is an addition reaction in which water is added to an unsaturated compound such as an alkene

What are the three addition reactions undergone by alkenes, and what products do they form?

1. Hydrogenation: reaction with hydrogen to form alkanes.

2. Halogenation: reaction with halogens ro form Dihaloalkane.

3. Hydration: reaction with water to form alcohols.

What is an isomer ?

Isomers are compounds with the same molecular formula but different structural formulae.

What are some harmful health effects associated with excessive alcohol consumption?

• Brain damage

• Dementia

• Trembling hands

• Hallucinations

• Vomiting blood

What are common everyday and industrial uses of alcohols?

• fuels (because they are highly flammable and burn with clean flames),

• perfumes

• cosmetics

• medicines

• printing inks.

What is the functional group of alcohols?

The functional group is the hydroxyl group $-OH$

What is the general formula of Alcohols?

$$C_nH_{2n+1}OH$$

What is the functional group of Carboxylic Acids ?

The functional group is the carboxyl group $-COOH$

What is the general formula for Carboxylic Acids ?

$$C_nH_{2n+1}COOH$$

What is the trend in water miscibility and solubility for the first few alcohols?

As the size of the alcohol molecules increase, thier solubility and miscibility with water decrease

What are the everyday uses of carboxylic acids?

• Soaps

• Medicines

• Food Preservations

Which carboxylic acid is the main component of vinegar ?

Ethanoic Acid

CH3 COOH

What is a fuel ?

A substance that burns to realese oxygen

What are some example of fuels?

• Coal

• Wood

• Oil

• Gas

What is a Fossil Fuel ?

Fuels formed from the remains of living organisms over millions of years

What is Combustion ?

A reaction of a substance with oxygen giving out energy

What is incomplete combustion ?

Occurs when a fuel burns in insufficient supply of oxygen

What is produced when a hydrocarbon or alcohol burns in a plentiful supply of oxygen?

Carbon Dioxide and Water

What is produced when a hydrocarbon or alcohol burns in a limited supply of oxygen

Carbon Monoxide and Water

What is an exothermic reaction ?

A reaction which release energy to it's surroundings

What is an endothermic reaction ?

A reaction in which absorbs energy from it’s surroundings

What type of reaction is represented by this potential energy diagram?

exothermic reaction

What type of reaction is represented by this potential energy diagram?

endothermic reaction

What equation is used to calculate the quantity of heat energy released when burning a fuel ?

$E_h = c m \times \text{Δ}T$

Identify this experimental setup ?

Enthalpy of combustion apparatus.

• What are the 3 source of error and 3 improvements we can use for the Enthalpy Of Combustion apparatus

Source of error:

1. Heat escapes to the surrounding

Improvement:

• Use insulation around the container

Source of error:

2. The water is not heated evenly

Improvement:

• Stir the water using the thermometer to distribute the heat evenly

Source of error:

3. Draught causes heat to escape

Improvement:

• Use a draught shield around the apparatus without blocking the oxygen supply