Alcohols + Carboxylic acids - SC23

Question 1

what are organic compounds composed of?

Answer 1

have a central frame work of carbon atoms, onto which hydrogen + other atoms (eg. Ethanol) are attached

Question 2

How does ethanol differ from ethane?

Answer 2

by having additional oxygen atom
both have very different properties and differet homologous series of compounds
Ethane is alkane and ethanol is in the alchol series

Question 3

What chemical properties do all alcohols share?

Answer 3

• Produce C02 + H20 on complete combustion
• can be oxidised to form compounds called carboxylic acids
• react with reactive metals such as sodium, forming H+ gas as 1 product
• All contain 1 -OH functional group

Question 4

What is a functional group?

Answer 4

The atom/group of atoms in a molecule that is responsible for it’s main chem. reactions

Question 5

what are the uses of alchol?

Answer 5

solvent for cosmetics, medicinal drugs, varnishes, fuels (methanol/ethanol)

Question 6

how are scientists working on using renewable sources for alcohol fuels?

Answer 6

making propanol / butanol fuels by fermenting plant cellulose

Question 7

what is the functical group for alcohol?

Answer 7

-OH

Question 8

why do all alchols have similar chemical properties?

Answer 8

because they all contain 1 -OH functional group

Question 9

What is the aim of the combustion of alcohol practical?

Answer 9

investigating the temp rse produced in a known mass of water by combustion of alcohols

Question 10

what is the method for combustion of alcohol?

Answer 10

• Measure mass of alcohol burner + cap and record mass
• place alcohol burner on heat proof mat
• use measuring cyclinder to add 100cm3 of cold water to a flask
• record initial temperature with thermostat and clamp the flask above alchol burner
• Light wick on burner and allow water to heat up by 40C
• Replace cap on burner and measure+record temp of water
• measure mass of alcohol burner + cap again and record
• calculate mass of alchol burned to produce 1C rise in temp
• repeat with more alcohol

Question 11

Why does wine left in open air turn into vinegar? what type of reaction is it? why does it occur naturally?

Answer 11

reaction with ethanol + O2 - oxidation - due to presence of certain bacteria

Question 12

What are the 4 common alcohols?

Answer 12

ethanol, propanol, butanol, pentanol

Question 13

what are the 4 common carboxylic acids?

Answer 13

methanoic acid, ethanoic acid, propanoic acid, butanoic acid

Question 14

what is the functional group for carboxylic acids?

Answer 14

-COOH

Question 15

What is the general formula for carboxylic acids?

Answer 15

CnH2n+1COOH+

Question 16

how are carboxylic acids often formed?

Answer 16

gentle oxidation of alcohols using oxidising agents such as hot copper oxide

Question 17

What are the chemical properties of carboxylic acids?

Answer 17

• forms solutions with pH less than 7 (if soluble)
• react with metals to form a salt + hydrogen
• react with bases to form a salt + water
• react with carbonates to form salt, water and C02

Question 18

Why do carboxylic acids form salts?

Answer 18

in solutions this group forms a hydrogen ion while the rest of the molecule forms a negative ion that makes the salt.

Question 19

what happens in fermentation?

Answer 19

plant material containing sugars is mixed with water and yeast. Enzymes in the yeast turn the sugars into ethanol + carbon dioxide

Question 20

what is the word equation for fermentation?

Answer 20

glucose -> ethanol + carbon dioxide

Question 21

What must be controlled in fermentation so enzymes work their best?

Answer 21

pH and temp

Question 22

what do air locks do and why are air locks neccesary during fermentation?

Answer 22

air locks allow CO2 to escape while keeping the air out. this is neccesary because yeast fermentation is a type of anaerobic respiration that only occurs in absence of 02