23 - Alcohols & Carboxylic Acids Flashcards
What’s the functional group in alcohols?
-OH
How can alcohols be used to form alkenes?
Alcohols can be dehydrated to form alkenes
What does functional group mean?
The atom or group of atoms in a molecule that is responsible for its main chemical reactions
What is the general formula of alcohols?
What’s the molecular formula of alcohol?
What is the molecular formula of Methanol?
What is the structural formula of Methanol?
What is the molecular formula of Ethanol?
What is the structural formula of Ethanol?
What is the molecular formula of Propanol?
What is the structural formula of Propanol?
What is the molecular formula of Butanol?
What is the structural formula of Butanol?
What is the functional group in Carboxylic acids?
- COOH
What’s the general formula for carboxylic acids?
Any alcohol can be oxidised to form which product?
A carboxylic acid
What are the uses of ethanol?
- A fuel for vehicles
- Raw material for the chemical industry
- Alcoholic drinks
What is the Ethanol in alcoholic drinks made from?
Sugars
How can ethanol be produced?
- By fermentation with yeast
- Produced from carbohydrates
What conditions need to be met in order to produce ethanol by fermentation?
- Mixture must be kept warm (25-35 degrees Celsius)
- Under anaerobic conditions
- Sugars dissolved in water & mixed w/ yeast
How do you produce a concentrated solution of Ethanol?
Ethanol is separated from the reaction mixture using fractional distillation
* Water & ethanol are heated
* Ethanol evaporates first, cools & condenses
What percentage of alcohol concentration does fermentation produce?
15%
Why can fermentation only produce 15% concentrated alcohol?
Higher concentrations kill the yeast cells
Why must the mixture be kept warm & in anaerobic conditions when producing Ethanol?
Warm - so reaction is fast enough but yeast doesn’t denature
Anaerobic - Only Co2 & water would be produced if its in aerobic conditions
Why does ethanol evaporate before water in fermentation?
As the bp of ethanol is lower than water
What is an organic compound?
A compound that has a central framework of carbon atoms onto which hydrogen & other atoms are attached
Give some examples of organic compounds
- Methane
- Ethanol
What are the similar properties of alcohols?
- 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
What are some uses of alcohols?
- Solvents for cosmetics, medical drugs & varnishes
- Alcoholic drinks
- Methanol & ethanol are widely used as fuels (and can be made from renewable resources)
What’s the molecular formula for methanoic acid?
What’s the structural formula for methanoic acid?
What’s the molecular formula for ethanoic acid?
What’s the structural formula for ethanoic acid?
What’s the molecular formula for propanoic acid?
What’s the structural formula for propanoic acid?
What’s the molecular formula for butanoic acid?
What’s the structural formula for butanoic acid?
What are oxidising agents?
A substance that causes another substance to be oxidised in an oxidation reaction
What are the similar properties of carboxylic acids?
- 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
Why are the acidic properties present in carboxylic acids?
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
What can vinegar be used to test for?
Carbonate rocks like chalk & limestone (calcium carbonate)
What happens to wine if it is left open to the air?
It turns to vinegar due to a reaction between ethanol and oxygen
—> Product is ethanoic acid
Core practical: Combustion of alcohols
How would you measure the energy given out by combustion of different alcohols?
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
Core practical: Combustion of alcohols
What are the expected results of this practical?
Temp is raised more as chain length of alcohol increases
—> Bc combustion of longer chain alcohols releases more energy
