URGENT Edexcel science revision (C2 9th June)

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Asiangirl101
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How would I answer these questions:

1) explain why hydrogen is not in group 1? (2 marks)

2) How would you separate two Immiscible substances? (3 marks)

3) Explain how to separate the different components of air? (6 marks)

4) Describe the practical steps involved in producing a chromatogram for a dye? (6 marks)

Thank You!!
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SelfishWeiner
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1) It's properties are completely different to those of the Alkali metals (those in group 1).
2) Separating funnel; they'll separate into layers (the densest at the bottom). Use a tap on the bottom of the funnel to separate them individually.
3) Fractional distillation:
i: Filter air to remove dust
ii. Cool air to -200C -> CO2 freezes and is removed, water vapour condenses and is removed
iii. Heat the liquid air slowly in the fractioning column and it will separate out into 'layers' which leave through pipes
iv: Oxygen and argon leave together so another column is used to separate them

4)
i. On paper, draw a pencil base line with crosses and labels for each substance
ii. add a drop of each substance to each cross on the baseline
iii. add the paper to a container of solvent (e.g. water, ethanol); the level of solvent must be below the baseline
iv: the solvent will travel up the paper, taking the substances with it and separating them into their different chemicals
[v: the Rf value of each chemical = distance travelled by substance / distance travelled by solvent]

Hope this helps!
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jackyboy17
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Hey in C2 is chromotography an important topic as i have never seen it come up before and dont understand it at all...im scared it will come up as a 3 or even 6 mark question and ill have no clue what it is. Can someone explain it simply to me??
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Taran121
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Chromatography is used in forensics to find evidence or what pen was used to write something.it can be used to find out colourings in compounds such as ink,paints and foods. Some couloured compounds dissolve better in a solvent this means that because they have different solubilities, the difference is used to separate the different components of mixtures in chromatography. In paper chromatography the samples are placed near the bottom of a sheet of special paper the different components are carried by the solvent at different speeds ultimately separating them the paper is known as chromatogram.

Uses: maybe a possible question
> police are able to analyse samples of DNA to find suspects.
>analyse paints and dyes so that museums are able to mix exact copies of old paints and restore
old paintings.
>used for food standards to see if dyes in food are safe to consume.

You may also be asked about the Rf value this is the distance moved by the compound divided by the distance moved by the solvent

This is what the equation looks like remember it:

Distance moved by compound
-----------------------–-------------- = Rf value
Distance moved by solvent

Hope this helps
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DaEvertonian
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It isn't that important and basically all you have to know is that you put spots of ink on paper on a pencil line and roll the paper up and put in a solvent. Then the solvent travels up the paper taking all the ink with it and they both travel a certain distance, from this we can tell what the substance is by working out Rf, disgrace travelled by substance divided by distance travelled by substance
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