c0mmodity
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Hey, since I made a thread last time for Biology, thought I might as well make one for Chemistry.

This is mainly for 61 tomorrow

I know we'll have to label lab apparatus, read statistics, plot a graph and learn the ion tests. Anything else?
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amarakhan
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Does anyone have any notes, tips or advice on how to answer the very last question in a paper 6 where we have to describe an experiment?
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DhillonDodhia
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(Original post by amarakhan)
Does anyone have any notes, tips or advice on how to answer the very last question in a paper 6 where we have to describe an experiment?
It's usually titration, finding out strength/concentration of acids.
For titration:
Use same volume of the base e.g. NaOH, 10cm3
Use an indicator (add to base in flask)
Steadily drop acid from a burette into the flask till the solution becomes neutral (will be shown by the indicator) and note the volume of acid used.
Repeat with other acid using same volume of base.
Compare results, which one uses less acid is stronger acid.
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lidzxxx
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Hello!
I have just finished the exam - I'm guessing that you have too! How did you find it? I thought it was alright although the six mark question on the back was hard - not sure I got any marks for that one! What did you put?
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amarakhan
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(Original post by DhillonDodhia)
It's usually titration, finding out strength/concentration of acids.
For titration:
Use same volume of the base e.g. NaOH, 10cm3
Use an indicator (add to base in flask)
Steadily drop acid from a burette into the flask till the solution becomes neutral (will be shown by the indicator) and note the volume of acid used.
Repeat with other acid using same volume of base.
Compare results, which one uses less acid is stronger acid.
Okay thanks
How did everyone find it?
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whyistheskyblue
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(Original post by lidzxxx)
Hello!
What did you put?
Most people put either using a cruicible to ensure no smoke escapes and then measure the mass of the powder. However many others said to set up gas syringes in a similar way to testing the percentage of oxygen in air.
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DangerousBox
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(Original post by amarakhan)
Okay thanks
How did everyone find it?
I didn't feel it went that well personally. D: Had trouble with question at end and the cations.
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examhater44
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(Original post by whyistheskyblue)
Most people put either using a cruicible to ensure no smoke escapes and then measure the mass of the powder. However many others said to set up gas syringes in a similar way to testing the percentage of oxygen in air.
Find mass of smoke
Then do mass of smoke-mass of calcium granules to find the mass of oxygen that reacted
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amarakhan
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How do you find the mass of smoke? Very confused on measuring the mass of a gas
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CIEEXAMSHWE
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(Original post by whyistheskyblue)
Most people put either using a cruicible to ensure no smoke escapes and then measure the mass of the powder. However many others said to set up gas syringes in a similar way to testing the percentage of oxygen in air.
I'm not 100% sure, however, I think a crucible won't work as you needed to find the maximum mass of oxygen, if you use a crucible, you may find that there isn't enough oxygen or there is too much oxygen in the crucible. If you open the lid the gas would escape, it's a bad question, I don't know the answer.
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CIEEXAMSHWE
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(Original post by amarakhan)
How do you find the mass of smoke? Very confused on measuring the mass of a gas
You can't really determine the mass of gas on it's own, I don't think
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DJShaji
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Couple of questions

a) wtf was that first label in the simple distillation question. Was it a test tube? because I didn't know what else it could have been even if it had a hole in the middle :O

b) What collects first? Sure ethanol has a lower boiling point but it is "collected" in the beads....Surely water technically collects first in the beaker :/ idk

b) What the hell is the appearance of aqueous Chromium Bromide and how are we supposed to know

c) How did people answer the question about finding which one is more concentrated.....I wrote about connecting metal rods and a voltmeter. A higher voltage reading means its more concentrated as there are more dissociated H+ ions which can carry more charge
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igcsehater
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(Original post by DJShaji)
Couple of questions

a) wtf was that first label in the simple distillation question. Was it a test tube? because I didn't know what else it could have been even if it had a hole in the middle :O

b) What collects first? Sure ethanol has a lower boiling point but it is "collected" in the beads....Surely water technically collects first in the beaker :/ idk

b) What the hell is the appearance of aqueous Chromium Bromide and how are we supposed to know

c) How did people answer the question about finding which one is more concentrated.....I wrote about connecting metal rods and a voltmeter. A higher voltage reading means its more concentrated as there are more dissociated H+ ions which can carry more charge

a) fractionating column
b) yeah ethanol first because it has lower boiling point
b) no idea?!!
c) yeah that sounds right. I just did simple acid plus metal gives hydrogen, the one that produces more hydrogen is more concentrated
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_lotty_
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Was anyone else not taught the Chromium chloride cation tests??!
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msmeme
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(Original post by CIEEXAMSHWE)
I'm not 100% sure, however, I think a crucible won't work as you needed to find the maximum mass of oxygen, if you use a crucible, you may find that there isn't enough oxygen or there is too much oxygen in the crucible. If you open the lid the gas would escape, it's a bad question, I don't know the answer.
Our chemistry teacher thinks it was the crucible experiment. You were supposed to open and close the lid periodically since it's a vigorous reaction but make sure the smoke doesn't escape.


Does anyone know the appearance of aq. chromium chloride? lol.

the rest of the paper was pretty easy but what effect does increasing the temperature have on the results of titration? i wrote no effect, anyone else?
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DhillonDodhia
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Test was fine except last question
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examhater44
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(Original post by CIEEXAMSHWE)
You can't really determine the mass of gas on it's own, I don't think
Yea u can lol
Mass of gas syringe by itself
mass of gas syringe plus smoke
mass of smoke = mass of gas syringe plus smoke-Mass of gas syringe by itself
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examhater44
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(Original post by msmeme)
Our chemistry teacher thinks it was the crucible experiment. You were supposed to open and close the lid periodically since it's a vigorous reaction but make sure the smoke doesn't escape.


Does anyone know the appearance of aq. chromium chloride? lol.

the rest of the paper was pretty easy but what effect does increasing the temperature have on the results of titration? i wrote no effect, anyone else?
Its green
and yea its no effect
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DhillonDodhia
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(Original post by igcsehater)
a) fractionating column
b) yeah ethanol first because it has lower boiling point
b) no idea?!!
c) yeah that sounds right. I just did simple acid plus metal gives hydrogen, the one that produces more hydrogen is more concentrated

its not the most hydrogen, its the one that produces hydrogen at the quickest rate
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examhater44
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(Original post by DhillonDodhia)
its not the most hydrogen, its the one that produces hydrogen at the quickest rate
Just say that the one that produces the most vigorous effervescence is the acid that is more concentrated
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