Originally posted by mercury
regarding this prac, you will just need to know the method, the reaction/equation, and under what conditions fermentation can take place.
There is no point knowing exact figures - ah, and also the other things for pracs in general: risk assessment, validity, reliability, etc.
yep. i made this random crap up for the hsc... never even done experiment at school:
3.3.4 Solve problems, plan and perform a first-hand investigation to carry out the fermentation of glucose and monitor mass changes.
Procedure:
Yeast was added to a stoppered flask with a sugar (fruit juice) solution
A delivery tube is connected to a beaker of limewater (saturated Ca(OH)2 solution)
Both the fermentation flask and limewater beaker are weighed and the mass recorded
The fermentation flask was kept at 30oC and air tight
The equipment was left to stand in prep-room and re-weighed after 48 hours
Distillation is performed to extract ethanol from the fermentation, mixture heated at about 78oC ethanols boiling point
A sample of the final product is combusted to conform the ethanol produced
Result:
CO2 produced turned limewater milky
The final product formed undergoes spontaneous combustion (proving that it is an alcohol and not just water)
The loss of mass in the fermentation flask equal to the gain of mass in the limewater beaker
Conclusion:
C6H12O6(aq) + (yeast provide enzymes) → 2CH3CH2OH(aq) +2CO2(g) + Heat
CO2(g) + H2O(l) → H2CO3(aq) → 2H+(aq) + CO3-2(aq)
Ca2+(aq) + CO32-(aq) → CaCO3(s)
Solve problems:
Keep the fermentation at about 30oC
o This is about the optimal temperature needed for fermentation to occur
o Above this elevated temperature, significant evaporation of water and hence more mass loss occurs
Lost of water
o Carry out the fermentation in a gas tight container with a pipe into a beaker of limewater
o This prevents the loss of mass as the water vapour is also collected with the CO2
Yeast used can not survive at above 15% ethanol content
o It is necessary to distil the liquid to obtain higher contents of ethanol
Difficulty in distilling the ethanol produced
o Boiling chips (porous ceramic material) is added to disperse the heat evenly to minimise the unwanted evaporation of water
Ensuring all equipment is sterile to begin with
Safety and risks:
Ingestion of ethanol can cause nausea, vomiting and inebriation
Ethanol is highly flammable
Safe work practice:
Remove all sources of unintended ignition from the working area
Do not ingest the alcohol produced
Work near readily supplies of water to put out fire
use it fuckfoot, if you need it... got no results though, sorry.
