Titration tips for tuesday peps:
1) Take the funnel out of the burret after filling
2) Record results to 2 dp always the last number must end in a 5 or 0.
3)As soon as there is a colour change stop and mix the concial flask. If the colour stays the same finsh and record ur result. If it doesnt add drops from the burrete.
Feel free to add more
wash down side of conical flask with water
be accurate on making the solution and the bottom of the meniscus has to be sitting on the the line
remember has to be distilled water, cos normal water has ions wich could mess up the experiment.
(Original post by snake)
wash down side of conical flask with water
Air-bubbles... remove them beforehand! then re-fill burette if you have to.
Read the meniscus at eye-level.
Remove the funnel before titrating.
Your 1st titration should be a rough one: allow 1 cm3 at a time, stop/ start flow method. This is to save time and know roughly around what value the end point titre should be. Remember to swirl the mixture.
For the 2nd titration add the acid in the burette dropwise to the alkali when nearing the rough titration value.
Titrate again. When you have 2 concordant values (within 0.10 cm3 of eachother) stop titrating.
There are 5 attempts max. If you don't find a concordant value by the 5th attempt, make it up!
Questions: when you run acid through the burette to 'clean it' does this mean you have to do the whole 'twirl it 360 degrees' number, or can you just let it run through into a beaker whilst it's clamped in place? Is running through the acid enough, do you have to clean it using distilled water as well?
Indicators: Methyl Orange or phenolphthalein. Do both fulfil the same role?
how do you remove air bubbles? what's good way of doing this? and how the hell do you do the planning section on AQA practical exam tips?
Is the exam deffo goin to be a titration? or wot else could it be?
(Original post by sonsta)
how do you remove air bubbles? what's good way of doing this? and how the hell do you do the planning section on AQA practical exam
To remove air bubbles, run the acid through the burette until the air bubble buggers off, then refill. I've heard of people flicking the burette, but I haven't tried that before so... not sure on that one.
For the glorious Practical... someone on another other thread believes that the plan involves a gas syringe. This means it could involve planning a rates of reaction experiment (varying concentration of reactants, or temperature : Ideal gas equation required here), or a 'prove that the molar ratio in the equation is correct'. Have a look at this http://www.zshare.net/download/gas-syringes-doc.html
Ofcourse whether the rumour is true or not is another thing!
reject anomolous results, preferably over a 0.1 cm cubed difference.
when you recieve your results, when working out and average, your average cannot be more accurate than a casual reading.
for example, 10.55cm3 & 10.65cm3 & 10.55cm3 will average out to 10.583333 cm3 on ur calculator.
THIS is more accurate than a normal titration. round up to 0.05cm3
e.g 10.583333 will become 10.60
when you record your results does the first one HAVE to be a rough titration? Or can you include it in your average titra value as long as it is concordant to the desired dp value? I mean will you get marked down if you use the first titration on the sheet?
Also are you really meant to record the second decimal place as a 0 or 5?
You wouldn't get marked down for saying 24.53 would you?
And yeah, when finding out the mean of the concordant and say you get 24.56666 you should DEFINITELY round to 24.55 or 24.57?
How close do the results have to be for the mean titre? Are they 0.10cm3 of each other or 0.05cm3 of each other?
look here for general tips: http://www.zshare.net/download/aqa-p...s-doc-s1n.html
tis the best revision thing I have seen
If all goes wrong, FIX YOUR RESULTS
Matchdancer, that link has just possibly saved my AS practical exam and thus my hoped for career in medicine... I salute you
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