16.1 - 17.2 Flashcards
What are 3 examples of greenhouse gases
1) CO2
2) water vapour
3) methane
What do greenhouse gases do
- absorb the radiation and re-emit it back towards the earth
What causes the increase of greenhouse gasses
- human activities(e.g burning fossil fuels and landfill)
What is global warming
- the gradual warming of the Earth
What is evidence for global warming
- analysing air and sea water samples
How do we reduce greenhouse emissions
- an international agreement was made so leaders of the countries who signed up would agree to limit CO2 emissions
How is the UK is trying to reduce emission levels
- by using more renewable energy sources: wind, solar and encouraging electric vehicle use
How does infrared spectroscopy use infrared radiation
- to increase the vibrational energy of covalent bonds in a sample
What two things does the frequency of infrared radiation absorbed by a covalent bond depend on
1) the ATOMS that are either side of the bond
2) the POSITIONs of the bond in the molecule
What are the uses of infrared spectroscopy
- BREATHALYSERS=> police use it to detect if someone is over the drink drive limit, we are measuring the amount of ethanol in a sample of breath, measure if the C-H peak
- EMISSION TESTING=> used to test car emissions, show levels of NO and CO
What is mass spectrometry used to find
- the relative molecular mass of a compound
What do peaks show in mass spectroscopy
- fragments of the original molecule
What relevance to the molecule does the last peak have
- is the same as the relative molecular mass of the molecule
What is fragmentation and what can it be used to determine
- the breaking up of molecules as they are bombarded with high energy electrons
- can be used to determine molecular structure
What type of charge does is detected in mass spectroscopy
- ONLY the positive charge
What 3 major peaks would the spectrum produce with propane
1) CH3CH2CH3 +
2) CH3 +
3) CH3CH2 +
When trying to work out an unknown compound what would you use
- both mass spectrometry and infrared
How do you identify an unknown compound
1) Work out the molecular formula
2) Distinguish the functional groups using infrared
3) Work out the structure using fragment pattern in mass spectrometry
When do you use reflux
- when you want to heat volatile liquids
What does reflux reactions allow for and how
- for you to heat without loosing your product
- it does this because the compounds can evaporate and condense and fall back into the flask
How do we heat up flammable liquids for reflux reactions and why
- using a water bath
- electric heater (mantle)
- because this is safer than using a naked flame
When do we use distillation
- when we want to separate substances with different boiling points
How does knowing the billing point of the chemical you want useful
- as it allows you to decide how you are going to separate your compound
What does you do when you the compound you want has a lower boiling point when distilling
- heat to the temperature of the boiling point of your compound you want to separate and collect the product in a separate vessel
What does you do when you the compound you want has a higher boiling point when distilling
- heat to the temperature of the boiling point of your compound you want to separate
- your compound will remain in the round bottomed flask
How is distillation useful
- when you want to extract a chemical before it reacts any further ( like an aldehyde)
E.g oxidising primary alcohols
When do we use re distillation and separation
- when we want to purify volatile substances which can be purifies further using separation
What is redistilation
- distilling a product
- and distilling the liquids again
Why do we use a separating funnel
- to separate and further purify substances
- and then add a drying agent to remove water
What are separation techniques used for
- to remove impurities that are dissolves in water
Describe the separation and purification method
1) add products from distillation into a separating funnel
2) add water to dissolve soluble impurities and create an aqueous solution
3) after allowing the solution to settle, 2 layers will form
4) drain the aqueous layer off
PURIFICATION
5) take impurities from he separating funnel and add to a round bottomed flaks
6) add anhydrous CaCl still it stops clumping together, this is a dehydrating agent and will remove any aqueous substances still remaining
7) invert the flask and leave it for 20-30 mins
8) filter the solid drying agent to remove
What does the top layer formed in separation show
- impure products
What does the bottom layer formed in separation show
- aqueous layer containing water soluble impurities
Draw an organic synthesis diagram
What has an influence on the type of reaction you get
- the functional group
What properties make alkanes react the way they do
- C-C
- unreactive & non poplar
- undergo radical substitution
What properties make alkenes react the way they do
- C=C
- non-polar & electron rich double bond
- undergo electrophilic addition
What properties make alcohols react the way they do
- C-OH
- polar C-O bond
- undergo nucleophillic substitution/ elimination/ dehydration
What properties make carboxylic acids react the way they do
- -COOH
- carbon electron deficient (delta positive)
What properties make haloalkanes react the way they do
- C-X
- polar C-X bond
- undergo nucleophilic substitution
What properties make aldehydes/ketones react the way they do
- C=O
- polar C=O bond
- aldehydes oxidise ketones don’t
