23 - Alcohols & Carboxylic Acids

Question 1

What’s the functional group in alcohols?

Answer 1

-OH

Question 2

How can alcohols be used to form alkenes?

Answer 2

Alcohols can be dehydrated to form alkenes

Question 3

What does functional group mean?

Answer 3

The atom or group of atoms in a molecule that is responsible for its main chemical reactions

Question 4

What is the general formula of alcohols?

Answer 4

Question 5

What’s the molecular formula of alcohol?

Answer 5

Question 6

What is the molecular formula of Methanol?

Answer 6

Question 7

What is the structural formula of Methanol?

Answer 7

Question 8

What is the molecular formula of Ethanol?

Answer 8

Question 9

What is the structural formula of Ethanol?

Answer 9

Question 10

What is the molecular formula of Propanol?

Answer 10

Question 11

What is the structural formula of Propanol?

Answer 11

Question 12

What is the molecular formula of Butanol?

Answer 12

Question 13

What is the structural formula of Butanol?

Answer 13

Question 14

What is the functional group in Carboxylic acids?

Answer 14

• COOH

Question 15

What’s the general formula for carboxylic acids?

Answer 15

Question 16

Any alcohol can be oxidised to form which product?

Answer 16

A carboxylic acid

Question 17

What are the uses of ethanol?

Answer 17

• A fuel for vehicles
• Raw material for the chemical industry
• Alcoholic drinks

Question 18

What is the Ethanol in alcoholic drinks made from?

Answer 18

Sugars

Question 19

How can ethanol be produced?

Answer 19

• By fermentation with yeast
• Produced from carbohydrates

Question 20

What conditions need to be met in order to produce ethanol by fermentation?

Answer 20

• Mixture must be kept warm (25-35 degrees Celsius)
• Under anaerobic conditions
• Sugars dissolved in water & mixed w/ yeast

Question 21

How do you produce a concentrated solution of Ethanol?

Answer 21

Ethanol is separated from the reaction mixture using fractional distillation
* Water & ethanol are heated
* Ethanol evaporates first, cools & condenses

Question 22

What percentage of alcohol concentration does fermentation produce?

Answer 22

15%

Question 23

Why can fermentation only produce 15% concentrated alcohol?

Answer 23

Higher concentrations kill the yeast cells

Question 24

Why must the mixture be kept warm & in anaerobic conditions when producing Ethanol?

Answer 24

Warm - so reaction is fast enough but yeast doesn’t denature

Anaerobic - Only Co2 & water would be produced if its in aerobic conditions

Question 25

Why does **ethanol** evaporate before water in **fermentation**?

Answer 25

As the bp of ethanol is lower than water

Question 26

What is an **organic compound**?

Answer 26

A compound that has a central framework of carbon atoms onto which hydrogen & other atoms are attached

Question 27

Give some *examples* of **organic compounds**

Answer 27

* Methane * Ethanol

Question 28

What are the **similar properties** of alcohols?

Answer 28

* Produce Co2 & water on complete combustion * Can be oxidised to form carboxylic acids * React w/ reactive metals, forming hydrogen as one of the gas products

Question 29

What are some **uses** of **alcohols**?

Answer 29

* Solvents for cosmetics, medical drugs & varnishes * Alcoholic drinks * Methanol & ethanol are widely used as fuels (and can be made from renewable resources)

Question 30

What's the **molecular formula** for **methanoic acid**?

Answer 30

Question 31

What's the **structural formula** for **methanoic acid**?

Answer 31

Question 32

What's the **molecular formula** for **ethanoic acid**?

Answer 32

Question 33

What's the **structural formula** for **ethanoic acid**?

Answer 33

Question 34

What's the **molecular formula** for **propanoic acid**?

Answer 34

Question 35

What's the **structural formula** for **propanoic acid**?

Answer 35

Question 36

What's the **molecular formula** for **butanoic acid**?

Answer 36

Question 37

What's the **structural formula** for **butanoic acid**?

Answer 37

Question 38

What are **oxidising agents**?

Answer 38

A substance that causes another substance to be oxidised in an oxidation reaction

Question 39

What are the **similar properties** of **carboxylic acids**?

Answer 39

* Form solutions with a pH of less than 7 (if soluble) * React w/ metals to form salt & hydrogen * React w/bases to form salt & water * React w/carbonates to form salt, water & Co2

Question 40

Why are the **acidic properties** present in **carboxylic acids**?

Answer 40

Due to the -COOH group In solution, this group forms a hydrogen ion while the rest of the molecule forms the negative ion that makes the salt

Question 41

What can **vinegar** be used to **test for**?

Answer 41

Carbonate rocks like chalk & limestone (calcium carbonate)

Question 42

What happens to **wine** if it is **left open to the air**?

Answer 42

It turns to vinegar due to a reaction between ethanol and oxygen ---> Product is ethanoic acid

Question 43

# Core practical: Combustion of alcohols How would you measure the **energy given out by combustion** of **different alcohols**?

Answer 43

1) Measure the mass or an alcohol burner & cap. Record the mass & name of the alcohol 2) Place alcohol burner in the centre of a heat resistant mat 3) Use a measuring cylinder to add cold water to a conical flask 4) Measure & record initial temp of water. Clamp flask above Bunsen burner 5) Light the wick of burner & allow water to hear up by 40 degrees 6) Replace cap on burner & measure final temp of water 7) Measure mass of alcohol burner & record mass 8) Calculate mass of alcohol burned to produce a 1 degree rise in temp

Question 44

# Core practical: Combustion of alcohols What are the **expected results** of this practical?

Answer 44

Temp is raised more as chain length of alcohol increases ---> Bc combustion of longer chain alcohols releases more energy