Flashcards in Ethene Deck (22):
Purpose of glass wool?
Holds ethanol in place
Avoids wetting alluminium oxide
Soaks up ethanol
Why is the glass wool added after ethanol?
To soak up ethanol completely
Appearance of aluminium oxide?
Two functions of aluminium oxide
Catalyst and dehydrating agent
Term used to describe reaction
Why is ethanol not heated directly?
Alcohol will evaporate too quickly
Keep ethanol away from flame - flammable
Remove delivery tube from water before you stop heating to prevent suck back
Avoid inhaling glass wool
What is suck back?
Air inside the boiling tube contracts which gives rise to a partial vacuum
How do you avoid suckback?
Remove delivery tube from water before heat is stopped
Why do you do discard the first test tube?
Consists mainly of air that has been displaced
What is unsaturation?
When a compound has carbon carbon double/triple bonds and does not contain the max amount of hydrogens it can contain
Give two tests for unsaturation?
Bromine water is added by drops to the test tube of gas. The test tube is stoppered and shaken - brown/red to colourless
Saturated - no colour change
Acidified kMnO4 - purple to colourless
Give an equation to show what happens with bromine water?
What happens when ethene is burned?
Clear luminous flame
Equation for the combustion of ethene
C2h4 + 3O2 = 2CO2 + 2H20 and heat
Two uses of ethene
Speed up ripening of fruit
Manufacturing of plastics
Give the equation for the preparation of ethene
C2H5OH = C2H4 + H20
At what stage is “suck back” most likely to occur?
When heat is removed
Give one possible consequence of a suck back occurring
Air inside boiling tube contracts as it cools - cold water is sucked into test tube and test tube cracks
Assuming this percentage yield of 60%, what is the maximum number of 75cm^3 test tubes of ethene gas that could be collected at room temperature and pressure when 2.4cm^3 of ethanol and density 0.8g\cm^3 react?
exam papers - 2012
multiply density by volume to get mass of ethanol
divide by mr of ethanol to get moles
using mole hopping, moles of ethanol = moles of ethene
multiply by mr of ethene to get grams
use formula - % yield = actual yield
theoretical yield x100
multiply by ROOM TEMP = 24,000cm
and divide by the 75cm^3 test tubes
Describe a chemical test to distinguish between samples of ethene and ethene
Bromine water [brown-colourless] UNSATURATION