Organic Families (Cambridge (CIE) IGCSE Chemistry)

Fuel oil is used for ships & power stations.

False.

Naphtha is used as a chemical feedstock.

Kerosene is used as jet fuel (paraffin).

The fraction used as a fuel in cars is petrol / gasoline.

The fraction used for surfacing roads is bitumen.

Fractions condense inside the fractionation tower because their vapours rise and reach a point where the temperature is below their boiling point.

As the molecules get larger, the intermolecular forces of attraction between the molecules becomes greater so more energy is needed to overcome them.

A hydrocarbon is a compound made up of hydrogen and carbon only.

Three fossil fuels are:

• Coal

• Natural gas

• Petroleum

False.

The main constituent of natural gas is methane.

Saturated means the compounds only have single carbon-carbon bonds, with no double bonds.

False.

Alkanes are generally unreactive compounds.

The alkane that is predominantly present in natural gas is methane.

Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation.

The equation for methane reacting with bromine in the presence of UV light is:

CH₄ + Br₂ → CH₃Br + HBr

The equation for methane reacting with chlorine in the presence of UV light is:

CH₄ + Cl₂ → CH₃Cl + HCl

The condition required for the reaction between alkanes and halogens is ultraviolet radiation / UV light.

False.

The products of complete combustion of an alkane are carbon dioxide and water.

True.

Ultraviolet light provides the activation energy for the photochemical reaction of an alkane with a halogen.

The haloalkane produced by methane reacting with chlorine in the presence of UV light is:

The haloalkane produced by ethane reacting with bromine in the presence of UV light is:

Three reactions that alkanes can undergo are:

• Combustion

• Cracking

• Substitution reactions with halogens

The balanced equation for the combustion of methane is:

CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)

All alkenes contain a double carbon bond, which is shown as two lines between two carbon atoms (C=C).

The double carbon bond (C=C) is the functional group in alkenes.

An alkene is a hydrocarbon compound containing at least one carbon-carbon double bond.

A double bond is a covalent bond formed by sharing two pairs of electrons between atoms.

An unsaturated compound contains double or triple bonds, which can undergo addition reactions.

False.

Alkenes are more reactive than alkanes due to the presence of the carbon-carbon double bond.

False.

The bromine water test can only distinguish between alkanes and alkenes due to their different reactivity with bromine, so it can't distinguish between propane and ethanol.

The colour change for the following reaction is orange to colourless.

Catalytic cracking is a process used to convert longer-chain molecules into hydrocarbons that are:

• Shorter chain.

• Higher demand.

• More useful.

The products of catalytic cracking are shorter chain alkanes, alkenes, and hydrogen

The conditions for catalytic cracking are:

• 600 – 700°C.

• A catalyst of alumina or silica.

Alkenes can be distinguished from alkanes using bromine water.

Alkenes will decolorise bromine water, while alkanes will not.

Bromine water is a brown / red-brown colored solution.

False.

When bromine water is shaken with an alkene, the solution will go colorless.

The reaction between bromine and propene is an example of an addition reaction.

An addition reaction is a reaction in which atoms of a simple molecule add across the C=C double bond of an alkene

In an addition reaction, only one product is formed

When bromine is added to an alkene, the two bromine atoms add across the carbon-carbon double bond to form a saturated compound.

When alkenes undergo addition reactions with hydrogen, an alkane is formed.

The reaction between alkenes and hydrogen requires a nickel catalyst.

When alkenes undergo addition reactions with steam, an alcohol is formed.

The reaction between alkenes and steam is also called a hydration reaction.

The reaction between alkenes and steam requires an acid catalyst.

True.

In the reaction between ethene and steam, ethanol is produced.

Ethanol can be synthesised by the hydration of ethene.

The conditions required for the hydration of ethene are a temperature of around 300°C, pressure of 60-70 atm, and a concentrated phosphoric acid catalyst.

Ethene is separated first due to its much lower boiling point, then ethanol and water are separated by fractional distillation.

The equation for the hydration of ethene is:

CH₂=CH₂ + H₂O → CH₃CH₂OH

Ethanol is produced by fermentation through yeast enzymes breaking down sugar or starch in the absence of oxygen to produce ethanol and carbon dioxide:

C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH

A chemical reaction in which a water molecule is added to a compound.

A process in which yeast or bacteria convert carbohydrates into alcohol or acids in the absence of oxygen.

False.

Fermentation is an anaerobic process that does not require oxygen for ethanol to be produced.

The fermentation of glucose requires:

• A temperature between 25 and 35 °C.

• The absence of oxygen.

• The presence of a yeast catalyst.

The equation for the fermentation of glucose is:

C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH

Comparing fermentation and hydration of ethene in terms of:

• Raw materials - fermentation uses renewable resources, while hydration uses non-renewable resources.

• Rate of reaction - fermentation is slow, while hydration is fast.

• Product purity / quality - fermentation produces an impure dilute product, while hydration produces pure ethanol.

False.

Fermentation is a batch process and hydration of ethene is a continuous process.

Hydration of ethene requires high temperature to produce ethanol.

A carboxylic acid is a compound containing the functional group carboxyl, -COOH.

Vinegar is an aqueous solution of ethanoic acid and contains about 5% of the acid by volume.

The molecular formula of ethanoic acid is CH₃COOH.

The name of the following carboxylic acid is propanoic acid.

The functional group of carboxylic acids is -COOH.

When carboxylic acids react with metals, a salt and hydrogen gas are produced.

When carboxylic acids react with carbonates, a salt, water, and carbon dioxide gas are produced.

When carboxylic acids react with bases, a salt and water are produced.

The names of salts formed by carboxylic acids all end in -anoate

The equation for the reaction between ethanoic acid and magnesium is:

2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂

The reaction between potassium hydroxide and propanoic acid is a neutralisation reaction.

The word equation for the reaction between potassium carbonate and butanoic acid is:

False.

The salts formed by methanoic acid are called methanoates.

Ethanoic acid can be prepared by oxidising ethanol with acidified potassium dichromate solution.

During the oxidation of ethanol to ethanoic acid, the potassium dichromate solution changes from orange to green.

The symbol equation for the oxidation of ethanol to ethanoic acid is:

CH₃CH₂OH + O₂  →  CH₃COOH + H₂O

False.

The oxidation of ethanol to ethanoic acid is a slow reaction and requires heating to its boiling point for about an hour.

The two methods used to make carboxylic acids are:

• Oxidation by fermentation.

• Using oxidising agents.

When ethanol undergoes microbial oxidation, a weak solution of vinegar (ethanoic acid) is produced.

Potassium manganate(VII) can be used as an oxidising agent to produce ethanoic acid.

An esterification reaction is a reaction between an alcohol and a carboxylic acid to form an ester.

The functional group of esters is R-COO-R.

An acid catalyst, typically concentrated sulfuric acid, is required for an esterification reaction.

The equation for the esterification reaction between ethanoic acid and ethanol is:

CH₃COOH (aq) + C₂H₅OH (aq) ⇌ CH₃COOC₂H₅ (aq) + H₂O (l)

Esters are named by combining the name of the alcohol (ending in -yl) and the name of the carboxylic acid (ending in -oate)

The ester formed from pentanol and butanoic acid is called pentyl butanoate.

False.

Butyl methanoate is made from methanoic acid and butanol.