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Predictions 15th June AQA CHEM unit 2 and 3 exam

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I really don't get titration o.O when someone says that word, my mind goes blank. I don't know what it is, what it's used for, why it's used. Any help? My chemistry is awful. :absinth:
Reply 21
Avatar for RAVVVo
RAVVVo
i think the 6 marker for c2 might be on crystallisation
Original post by RAVVVo
i think the 6 marker for c2 might be on crystallisation


That would be alright
Original post by onifernando
Explain why scientists regarded a periodic table ofthe elements first as a curiosity, then as a useful tooland finally as an important summary of the structureof atoms?


How would you answer that question?
Original post by tomo_nufc
Just say that opposite charges attract each other and so positive ions go to the negative electrode and negative ions go to the positive electrode. You will get quite a lot of marks for saying that.

Also as electrons are negative charge, then the positive ions will gain electrons (be reduced) to become pure and negative ions will lose electrons (oxidised) to become pure.


Thank you so very much!!!!
Does anyone have any quick tips or anything because I'm so not gonna pass this C3 exam
Original post by penelopecrux
Adam, i really can't tell you what's on the whole exam, just revise what I told u about, ok? AND GOOD LUCK, HOPE U GET A*!

Is there anything to revise apart form that
Original post by Anygy
I really don't get titration o.O when someone says that word, my mind goes blank. I don't know what it is, what it's used for, why it's used. Any help? My chemistry is awful. :absinth:


Titration is used to work out the amount of alkali needed to neutralise an acid ( or the other way around)
The method is:
1. Put 50cm^2 of acud in a conical flask
2. Put indicator (phenolphthalein) in the alkali and mix it, should go purple
3. Full the burette with acid (making sure the tap is full)
5. Put the conical flask ob top of a white tile to see the colour change(optional)
4. Open the tap with one hand and swirl the conical flask with other hand to mix the alkali and acid together
5. Close the tap when the solution in the conical flask goes colourless
6. Work out how much acid was used by substracting the end reading of the burette from the initial reading(eg: initial reading 25cm^2, and end reading 11cm^2. Working out: 25-11=14cm^2 used to neutralise the alkali)

From this you can then work out the concentration of one of the 2 (alkali or acid) if you know the 2 of the folowing things about the other one:
Concentration
Moles
Volume
(usually you will be given concentration and volume and you have to work out concentration. Conc=mol/vol)
Once u get the moles of one substance, you need to work ou the ratio so you need to look at the balanced equation..... Look at the picture (sorry cant explain the last part so well but its on the pic)

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1465942831898.jpg49.3KB
Can someone please explain crystallisation for me? As a 6 marker?
Original post by Yasminxb
Can someone please explain crystallisation for me? As a 6 marker?


Is that unit 2? I am only doing unit 3 and really cant remember what i did last year in additional

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Original post by Yasminxb
Can someone please explain crystallisation for me? As a 6 marker?

Sure here it is
There are two types of crystallization reactions. (they form crystal salts)

Acid = Nitric, Hydrochloric, Sulfuric
Base/Alkali = Metal Oxide or Metal Hydroxide

1) Acid + Insoluble Base -----> Salt + Water ( I will use copper oxide with sulfuric acid as an example)
Copper oxide + Sulfuric Acid -----.> Copper Sulfate + Water

1)- Add copper oxide to sulfuric acid in a beaker
- Heat the mixture - this increases the rate of reaction- and stir it.
- Until you can see copper oxide remains in the solution (that way you know the reactants have been used up)

2)- Place some filter paper over a funnel and a flask.
- Filter the Copper Sulfate solution through the filter paper
- This /filtration/ separates the copper oxide from the copper sulfate solution (which is now in the flask)

3)-Add your Copper sulfate solution to an evaporating dish
-Place it over a beaker of water
-Heat the water with a Bunsen burner
-Wait until half of the Copper sulfate solution has evaporated off. /evaporation/
-Let the evaporating dish sit in a cool, ventilated area for a few days until Copper Sulfate crystals form. /crystallization reaction/

OR

Acid + Alkali -----> Salt + Water
1) -Measure out volume of alkali in a beaker - e.g - 20cm3
-Add universal Indicator so the solution goes purple
-Then add acid, with a pipette until the solution turns GREEN /neutralization/.
-Write down the number of acid drops/ volume of acid you added.

2) -Repeat the experiment with the measured amounts of acid + alkali you used but DO NOT add universal indicator. /neutralization/

3)- Place solution in evaporating dish over beaker of water
-Heat the water with Bunsen Burner
-Allow half of the solution to evaporate off /evaporation/
- Place in cool, ventilated environment for a few days
-Solution (Salt) is crystallized /crystallization/.

bloody hell that took long to type :smile:, good luck with C2 everyone! x
Crystallization is unit 2 yes, I posted about it explaining the process x.
Original post by mediaya
Is that unit 2? I am only doing unit 3 and really cant remember what i did last year in additional

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Original post by crustyegg
Crystallization is unit 2 yes, I posted about it explaining the process x.


Thanks so much!
Original post by mediaya
Titration is used to work out the amount of alkali needed to neutralise an acid ( or the other way around)
The method is:
1. Put 50cm^2 of acud in a conical flask
2. Put indicator (phenolphthalein) in the alkali and mix it, should go purple
3. Full the burette with acid (making sure the tap is full)
5. Put the conical flask ob top of a white tile to see the colour change(optional)
4. Open the tap with one hand and swirl the conical flask with other hand to mix the alkali and acid together
5. Close the tap when the solution in the conical flask goes colourless
6. Work out how much acid was used by substracting the end reading of the burette from the initial reading(eg: initial reading 25cm^2, and end reading 11cm^2. Working out: 25-11=14cm^2 used to neutralise the alkali)

From this you can then work out the concentration of one of the 2 (alkali or acid) if you know the 2 of the folowing things about the other one:
Concentration
Moles
Volume
(usually you will be given concentration and volume and you have to work out concentration. Conc=mol/vol)
Once u get the moles of one substance, you need to work ou the ratio so you need to look at the balanced equation..... Look at the picture (sorry cant explain the last part so well but its on the pic)

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Oh my god, thanks so much <3 luckily it didn't come up :redface:
Original post by Anygy
Oh my god, thanks so much <3 luckily it didn't come up :redface:


it came up in my exam though:rolleyes:
Original post by mediaya
it came up in my exam though:rolleyes:


Did u do further additional? :eek:
Original post by Anygy
Did u do further additional? :eek:

yep, i guess you did triple science course?
there is 2 paper btw
further additional science C3 (the one i did)
chemistry C3
Original post by mediaya
yep, i guess you did triple science course?
there is 2 paper btw
further additional science C3 (the one i did)
chemistry C3


I did double science :biggrin: I don't have the brain capacity to do further additional ><
Original post by Anygy
I did double science :biggrin: I don't have the brain capacity to do further additional ><


so why did u ask about titrations? tha'st in futher additional, right?
Reply 39
Avatar for Cat112
Cat112
Unlucky hehe

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