Unit 2 - Topic 3 - Carboxylic Acids

Question 1

Describe vinegar

Answer 1

Vinegar is a dilute solution of ETHANOIC ACID. Its old name is ACETIC ACID.

Vinegar is used in household cleaning products and is a non-toxic acid so can be used safely in household situations.

Question 2

What are the -COOH group of atoms called?

Answer 2

Carboxylic group

This is called the functional group as it gives the molecule the chemical properties of a CARBOXYLIC ACID.

Question 3

Describe carboxylic acids

Answer 3

The carboxylic acids with a structure based on an alkane structure are called ALKANOIC ACIDS.

Question 4

What does the name of the ethanoic acid tell you?

Answer 4

How many carbon atoms it contains

That is has a single carbon to carbon bond

oic means that it contains a carboxyl group (-COOH)
The carboxyl group gives the molecule acidic properties

Question 5

Name the family of carboxylic acids

Answer 5

Alkanoic acids

Question 6

Describe the appearance (colour and state) of ethanoic acid

Answer 6

Colourless Liquid

Question 7

Describe the smell of ethanoic acid

Answer 7

Strong and Sharp

Question 8

Describe the conductivity of a solution of ethanoic acid

Answer 8

Insulator

Question 9

Describe the solubility in water of the alkanoic acids

Answer 9

Methanoic, ethanoic, propanoic, and butanoic acid are all miscible in water, thereafter the solubility decreases as the size increases

Question 10

Describe the pH (acidic, neutral, or alkaline) of ethanoic acid

Answer 10

Acidic

Question 11

Describe the reaction with magnesium of ethanoic acid

Answer 11

Reacts slowly making H2O

Question 12

Describe the reaction with marble (calcium carbonate) of ethanoic acid

Answer 12

Reacts slowly producing CO2

Question 13

Describe ethanoic acid

Answer 13

A solution of ethanoic acid contains ions.

With a pH less than 7, the solution contains the hydrogen ion (H+ ).

A solution of ethanoic acid reacts with magnesium and calcium carbonate showing it is a typical acid.

Question 14

How is etanoic acid formed?

Answer 14

Ethanoic acid is formed when ethanol undergoes mild oxidation. This reaction can happen in alcoholic drinks (e.g. wine or cider) when the ethanol reacts with oxygen from the air.

Question 15

Describe how alkanoic acids are made

Answer 15

Alkanoic acids are made when alcohols undergo a mild oxidation reaction.

The hydroxyl group (-OH) on the alcohol molecule has to be on the end of a carbon chain to produce a carboxyl group (-COOH) during mild oxidation.

Question 16

What is the general formula of the alkanoic acids based on?

Answer 16

The alkane general formula

Question 17

What is the general formula of the alkanoic acids?

Answer 17

CnH2n+1COOH

The n in the formula is not related to the carbon atoms indicated by the name, as there is a carbon atom in the carboxyl group

Question 18

Give the formula of methanoic acid

Answer 18

HCOOH

Question 19

Give the formula of ethanoic acid

Answer 19

CH_3COOH

Question 20

Give the formula of propanoic acid

Answer 20

C_2H_5COOH

Question 21

Give the formula of butanoic acid

Answer 21

C_3H_7COOH

Question 22

Describe the physical properties of the alkanoic acids

Answer 22

As the number of carbon atoms in the alkanoic acid molecule increases, the boiling point increases.

As alkanoic acids increase in size their melting and boiling points increase due to the increasing strength of the intermolecular forces of attraction between molecules.

The alkanoic acids have similar chemical properties and have a general formula showing they are a HOMOLOGOUS SERIES.

Question 23

Describe the reaction of carboxylic acids with metals

Answer 23

Metal + Acid –> Salt + Hydrogen

Carboxylic acids react with the more reactive metals to produce a salt and hydrogen. The reactions are just the same as with acids like hydrochloric acid, except they tend to be rather slower.

Question 24

Describe the reaction of carboxylic acids with metal hydroxides

Answer 24

Metal Hydroxide + Acid –> Salt + Water

These are simple neutralisation reactions and are just the same as any other reaction in which hydrogen ions from an acid react with hydroxide ions. They are most quickly and easily represented by the equation:
H+ (aq) + OH- (aq) –> H2O (l)

Question 25

Describe the reaction of carboxylic acids with carbonates and hydrocarbonates

Answer 25

Metal Carbonate + Acid --> Salt + Water + Carbon Dioxide In both of these cases, a salt is formed together with carbon dioxide and water You end up with a colourless solution.

Question 26

Describe the reaction of carboxylic acids with salts of carboxylic acids

Answer 26

Carboxylic acids are acidic because of the hydrogen in the -COOH group. When the acids form salts, this is lost and replaced by a metal.

Question 27

Give the uses of methanoic acid

Answer 27

In ant stings A preservative and antibacterial agent in feedstock

Question 28

Give the uses of ethanoic acid

Answer 28

Food flavouring - vinegar A food preservative - pickling

Question 29

Give the uses of butanoic acid

Answer 29

In butter, milk and cheese | Has a cheesy smell

Question 30

Give the formula of lactic acid

Answer 30

CH_3CHOHCOOH

Question 31

Give the uses of lactic acid

Answer 31

In sour milk, yogurt, and cheese Forms in our muscles during exercise

Question 32

What is the addition reaction called when you add water?

Answer 32

Hydration Reaction

Question 33

What is the addition reaction called when you add Hydrogen?

Answer 33

Hydrogenation Reaction

Question 34

What is the addition reaction called when you add any of the Halogens?

Answer 34

Halogenation Reaction

Question 35

What is the addition reaction called when you add Bromine?

Answer 35

Bromination Reaction

Question 36

What is the addition reaction called when you add Iodine

Answer 36

Iodination Reaction

Question 37

Describe the boiling/melting points of carboxylic acids

Answer 37

As the molecule gets larger, the number of carbons increase which means there are greater intermolecular forces of attraction between molecules. This means much more energy is needed to separate it resulting in a greater melting/boiling point.

Question 38

What is the functional group for carboxylic acids called?

Answer 38

Carboxyl Group

Question 39

What will happen if the hydroxyl group is not at the end of a carbon chain?

Answer 39

It will not form a carboxyl group during mild oxidation

Question 40

What will happen if the hydroxyl group is at the end of a carbon chain?

Answer 40

It will form a Carboxyl group during mild oxidation