AQA GCSE Chemistry - C2 & C3 (14th May 2015)

Reply 100

Muhammad Shafi

3

wot 6 mark question do u think goings to come up

Reply 101

XxRAEXx

1

I am certain that some sort of testing for ions will come up. It's such a massive section and they' we got loads of different subsections in it:/

Testing for ions some of these I think may come up:
Flame test
Sodium hydroxide test
Halide test
Carbonate test
Sulfate test
(They might be absolute pricks and make you use knowledge about 3 or 4 or these tests to answer a question?:/)

Reply 102

spnlove

3

Original post by Nai18

Also, can anyone post key points about the period table from Newlands and Mendeleev please?

Posted from TSR Mobile

Newlands' Law of Octaves:
- noticed every 8th element had similar properties so arranged elements in rows of seven according to atomic mass
- BUT pattern broke down in 3rd row due to transition metals
- Problems: groups contained elements which didn't have similar properties; he mixed up metals and non-metals; didn't leave any gaps for undiscovered elements

Mendeleev:
- arranged the known elements in order of atomic mass
- left gaps to keep elements with similar proplerties in same columns (the groups)
- he could predict properties of undiscovered elements from this

Hope that helps, if you have any questions feel free to ask :smile:

Reply 103

fabsafxo

3

Do thermosetting polymers have covalent bonds or intermolecular forces???

Like what are the crosslinks and where are the forces???

Thank youuu

Reply 104

XxRAEXx

1

Original post by Muhammad Shafi

wot 6 mark question do u think goings to come up

C3-
Could be-
describing a caliormetry/titration experiment
Testing for ions
Hard water/soft water and purification
Haber process
Explaining difference in reactivity of g1 &g7

C2:
Could be-
Reasons why chlorine is gas at room temperature but solid with sodium
Polymer
(Doubt it would electrolysis)
How metallic bonding/ionic bonding can
Conduct
Idk it's anyone's guess and with theb randomness of the biology ones.. It could be a comparison again? Just make sure you read all the sections especially the small ones !!!

Reply 105

spnlove

3

Original post by pollyy

Hi would anyone be able to explain to me how to do this question from the June 2013 C2 paper?

Write the formula of ammonium sulfate using the ion formulas on the data sheet.

The answer is (NH4)2SO4 but I can't work out how to get to that! Thank you!

Yeah, so on the data sheet you're given that the formula for ammonium ions is NH4+ and the formula for sulfate ions is SO4(2-). To get the formula you have to balance the charges so that there is a neutral charge overall. As the sulfate ions have a charge of negative 2 but the ammonium ions have a charge of positive 1, you need two ammonium ions to balance the charge of the sulfate ions.

Does that make sense? sorry i'm not very good at explaining!

Reply 106

sweetsss

3

do you think we would need to know the different rate of reaction experiments? eg the HCl and sodium thiosulphate one...

Reply 107

fabsafxo

3

Original post by XxRAEXx

C3-
Could be-
describing a caliormetry/titration experiment
Testing for ions
Hard water/soft water and purification
Haber process
Explaining difference in reactivity of g1 &g7

C2:
Could be-
Reasons why chlorine is gas at room temperature but solid with sodium
Polymer
(Doubt it would electrolysis)
How metallic bonding/ionic bonding can
Conduct
Idk it's anyone's guess and with theb randomness of the biology ones.. It could be a comparison again? Just make sure you read all the sections especially the small ones !!!

Hi, I only do C2.
I am sorry to ask this, but I am actually unsure as to why chlorine is gas at room temperature but solid with sodium???

Could you explain to me please thankyou!!xxxxx

Reply 108

fabsafxo

3

how can metallic bonding and ionic bonding conduct electricity???

Reply 109

spnlove

3

Original post by fabsafxo

Do thermosetting polymers have covalent bonds or intermolecular forces???

Like what are the crosslinks and where are the forces???

Thank youuu

Thermosetting and thermosoftening polymers both have strong covalent bonds but thermosetting polymers have weak intermolecular forces whereas thermosoftening polymers have strong intermolecular forces (the strong intermolecular forces can also be called crosslinks). Covalent bonds are between the atoms themselves but intermolecular forces are between the different molecules of those atoms. As thermosetting polymers have strong intermolecular forces this makes them have a solid structure and won't soften when heated as the forces would need a lot of energy to overcome.

Reply 110

fabsafxo

3

Original post by pollyy

Yeah I think I mentioned the cost of the plant would be too high, but also a lot of energy is required to provide high pressures, so that in itself is expensive too!

hi is that about C2 OR C3???

Reply 111

fabsafxo

3

Original post by spnlove

Thermosetting and thermosoftening polymers both have strong covalent bonds but thermosetting polymers have weak intermolecular forces whereas thermosoftening polymers have strong intermolecular forces (the strong intermolecular forces can also be called crosslinks). Covalent bonds are between the atoms themselves but intermolecular forces are between the different molecules of those atoms. As thermosetting polymers have strong intermolecular forces this makes them have a solid structure and won't soften when heated as the forces would need a lot of energy to overcome.

OMDS!!
Thankyou so much!!

Life saver over 'ere;D xxx

Reply 112

battenberg123

2

Pedictions for c3 tomorrow?

Reply 113

mghp

3

Original post by brozza981

Positive Ions Flame Test:
PoP CaR BaG LiC SoY
Potassium - Purple,
Calcium - Red,
Barium - Green,
Lithium - Crimson,
Sodium - Yellow!

Please don't tell me that's C2 :frown:

Reply 114

electrahearts

15

What kind of questions would come up for acids and bases? I'm still trying to get my head round it

Reply 115

zc555

2

Hi, I'm sorry to ask this but can someone go through the Titration, Halide, Sulfate and Sodium Hydroxide tests please. I'm really confused with them! :frown:

Reply 116

Louisbirch

Original post by mghp

Please don't tell me that's C2 :frown:

It's c3

Reply 117

pollyy

6

Original post by spnlove

Yeah, so on the data sheet you're given that the formula for ammonium ions is NH4+ and the formula for sulfate ions is SO4(2-). To get the formula you have to balance the charges so that there is a neutral charge overall. As the sulfate ions have a charge of negative 2 but the ammonium ions have a charge of positive 1, you need two ammonium ions to balance the charge of the sulfate ions.

Does that make sense? sorry i'm not very good at explaining!

Yes it does! Thank you, I think I just got confused because I always think of ammonia as NH3, but I understand now :smile:

Thanks!

Reply 118

pollyy

6

Original post by zc555

Hi, I'm sorry to ask this but can someone go through the Titration, Halide, Sulfate and Sodium Hydroxide tests please. I'm really confused with them! :frown:

Titration: Is used to find how much acid is needed to neutralise an alkali (or vice versa) which is then used to calculate an unknown concentration.
Did you want help with the calculation or the titration method?

As for the ion tests; to test for halides, add dilute nitric acid (not HCL as that contains chlorine which is a halide!) then add silver nitrate solution, and use the colour of the precipitate to distinguish between halides:
Chlorides- white precipitate
Bromides- cream precipitate
Iodides- yellow precipitates

Sulfate test: add dilute HCL then barium chloride solution, if a WHITE precipitate is formed, then the substance is a sulfate!

Sodium Hydroxide test (for metal ions): Add NaOH, then use colour of precipitate to distinguish-
Iron (II)- Green precipitate
Iron (III)- Reddish brown precipitate
Copper (II)- Light blue precipitate
Magnesium, Calcium and Aluminium ALL form white precipitates, but aluminium ions dissolve in excess NaOH into a colourless solution, and calcium ions can be distinguished through the flame test (red flame).

Hope this helps and I can try and help with titration too! :smile:

Reply 119

maxjackson5

2

This is what I think I know about polymers; is it correct?

Thermosoftening - Weak intermolecular forces between chains make it easy to seperate chains and this results in them having a low melting/boiling points so they can be melted and re-moulded.

Thermosetting - Strong covalent bonds between chains mean that chains are hard to seperate and therefore they have high melting/boiling points because large amounts of energy are required to break chains. Can't be melted and re-moulded

Is this correct? Anything to add? Thanks.

AQA GCSE Chemistry - C2 & C3 (14th May 2015)

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