carboxylics and asters

Question 1

Carboxylic acids are weaks or strong acids?

For example:

Answer 1

weak acids.

Question 2

Are weak acids are less or more reactive than strong acids.

Answer 2

Weak acids are less reactive than strong acids.

weak acids are less reactive than strong acids.

Question 3

Carboxylic acids show the normal characteristic reactions of acids. Reaction with metals

Answer 3

acid + metal → salt + hydrogen

Question 4

Give an example reaction using magnesium

Answer 4

ethanoic acid + magnesium → magnesium ethanoate + hydrogen

Question 5

Reaction with alkali

Answer 5

acid + soluble hydroxide → salt + water

Question 6

Given an example reaction with sodium hydroxide (alkali)

Answer 6

ethanoic acid + sodium hydroxide → sodium ethanoate + water

Question 7

Reaction with carbonate

Answer 7

acid + metal carbonate → salt + water + carbon dioxide

Question 8

Give an example reaction with carbonate

Answer 8

ethanoic acid + calcium carbonate → calcium ethanoate + water + carbon dioxide

Question 9

What are Carboxylic acids ?

Answer 9

Carboxylic acids are found in a number of natural and synthetic substances. They are weak acids and react with alcohols to form esters, which often have fruity smells. Fats and oils are naturally occurring esters which are used by plants and animals as an energy store.

Question 10

Carboxylic acids all contain the –? functional group?

Answer 10

Carboxylic acids all contain the –COOH group and this is generally responsible for their chemical properties and reactions.

Question 11

What are carboxylic acids named after?

Answer 11

They are named after their ‘parent’ alkanes, for example: methanoic acid (carboxylic acid) and methane (‘parent’ alkane), and ethanoic acid (carboxylic acid) and ethane (‘parent’ alkane).

Question 12

What is the structural formula of Methanoic acid?

Answer 12

Methanoic acid

HCOOH

Question 13

What is the structural formula of Ethanoic acid

Answer 13

CH3COOH

Question 14

Esters are formed when a …………….reacts with an ………… The general word equation is?

Answer 14

Esters

Esters are formed when a carboxylic acid reacts with an alcohol. The general word equation is:

carboxylic acid + alcohol → ester + water

Question 15

Esters have distinctive smells, which are often…… They are therefore used in the manufacture of what ?

Answer 15

Esters have distinctive smells, which are often fruity. They are therefore used in the manufacture of perfumes and food additives.

Question 16

Esters also used in ? .

Answer 16

solvents and plasticiers

Question 17

Fats and oils are ……………- ……………… esters of ……………… ………….. carboxylic acids with a special type of alcohol called ……….. oils are liquids. Animals and plants produce oils and fats as an energy store

Answer 17

Fats and oils

Fats and oils are naturally-occurring esters of three long carboxylic acids with a special type of alcohol called glycerol. Glycerol has three carbon atoms, each with an –OH group on.

Fats are solid at room temperature, whereas oils are liquids. Animals and plants produce oils and fats as an energy store

Question 18

Glycerol has how many carbon atoms?

Answer 18

three carbon atoms, each with an –OH group on.

Question 19

Fats are ….. at room temperature, whereas

Answer 19

Fats are solid at room temperature, whereas

Question 20

Animal fats (eg lard) usually contain a lot of …………… fats, which means that there are no……………………….bonds?

Answer 20

Saturated fats

Animal fats (eg lard) usually contain a lot of saturated fats, which means that there are no C=C double bonds

Question 21

Vegetable oils and fats usually contain a higher proportion of …………… molecules, which means that they contain …………….bonds?

Answer 21

Unsaturated fats and oils

Vegetable oils and fats usually contain a higher proportion of unsaturated molecules, which means that they contain one or more C=C bonds.

Question 22

What is hydrolysis of an ester. ?

Answer 22

Hydrolysis of fats and oils

Fats and oils contain ester links formed when glycerol has reacted with fatty acids. These ester links can be broken when they react with water, splitting the molecule back into an acid and an alcohol.

This process is known as hydrolysis of an ester. It can be described using the following word equation:

ester + water → acid + alcohol

Question 23

You can make a variety of esters by reacting different carboxylic acids with different alcohols. Give an example:

Answer 23

You can make a variety of esters by reacting different carboxylic acids with different alcohols. For example:

ethanol + ethanoic acid → ethyl ethanoate + water

Question 24

What is the first step in making an ester?

Answer 24

1. Add the correct carboxylic acid and alcohol to a flask, along with a few drops of concentrated sulfuric acid.

Question 25

What is the second step in making an ester?

Answer 25

2.
Fit a condenser vertically to the flask and heat the mixture strongly. This is called ‘heating under reflux’ because the vapours that evaporate are cooled and condense back into the flask.

Question 26

What is the third step in making an ester?

Answer 26

3.
The condenser is rearranged so that the mixture can be heated gently and the ester can then be distilled off from the remaining reactants and the water.

4.
The distillate is transferred to a separating funnel where aqueous sodium carbonate is added. This reacts with any remaining acid to neutralise it and remove it into the aqueous layer, which will be the lower (more dense) of the two liquids. The aqueous layer is then run off, leaving the ester in the upper (less dense) organic layer.

5.
The organic layer is then transferred to a flask and solid anhydrous calcium chloride is added to remove any remaining water. The calcium chloride is removed by filtration. A final distillation is then performed to obtain the pure ester.

Steps in making an ester
1.
Add the correct carboxylic acid and alcohol to a flask, along with a few drops of concentrated sulfuric acid.

2.
Fit a condenser vertically to the flask and heat the mixture strongly. This is called ‘heating under reflux’ because the vapours that evaporate are cooled and condense back into the flask.

3.
The condenser is rearranged so that the mixture can be heated gently and the ester can then be distilled off from the remaining reactants and the water.

Question 27

4.
The distillate is transferred to a separating funnel where aqueous sodium carbonate is added. This reacts with any remaining acid to neutralise it and remove it into the aqueous layer, which will be the lower (more dense) of the two liquids. The aqueous layer is then run off, leaving the ester in the upper (less dense) organic layer.

5.
The organic layer is then transferred to a flask and solid anhydrous calcium chloride is added to remove any remaining water. The calcium chloride is removed by filtration. A final distillation is then performed to obtain the pure ester.

What is the fouth step in making an ester?

Answer 27

4.
The distillate is transferred to a separating funnel where aqueous sodium carbonate is added. This reacts with any remaining acid to neutralise it and remove it into the aqueous layer, which will be the lower (more dense) of the two liquids. The aqueous layer is then run off, leaving the ester in the upper (less dense) organic layer.

Question 28

What is the fifth step in making an ester?

Answer 28

5.
The organic layer is then transferred to a flask and solid anhydrous calcium chloride is added to remove any remaining water. The calcium chloride is removed by filtration. A final distillation is then performed to obtain the pure ester.