AQA Chemistry 3

What I've covered in Chemistry 3 so far

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  • Created by: Ewan
  • Created on: 10-03-12 10:01

The Periodic table

The first person to classify elements was John Daton - listed them by mass

John Newlands - law of octaves

Meedendeleev was the founder of the "modern" periodic table - Elements organised by properties and listed by mass

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Group 7 reactivity

Displacement can be used to define the order of reativity

The further down the group you go the less reactive the atom

This is because the +ve nucleus is further away from the outer most energy level - Therefore it's harder to attract a negative electron because it's a greater distance from the nucleus so the attraction is weaker.

Also the other electrons "shield" the +ve charge

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Group 1 reactivity

The further down Group 1 you go the greater the reactivity

This is because they want to lose their electron in their outer energy shell and as the further down you go the weaker the force of attraction between the nucleus and the electron.

Commen properties of these metals are: they are kept under oil; shiny when freshly cut; they form alkalis when added to water and they quickly tarnish

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Titrations

Titrations are simply used in neutalization reaction. The burette is always filled with acid and it is always added to an alkali solution in a conical flask.

Acids always contains H+ ions and alkalis contain OH- ions

Strong Acids & Alkalis are ones which are 100% ionised in water

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Using Titrations to caluclate the concentration of

1st Step) Write the balanced neutralisation reaction equation

2nd Step) (known concentration/volume of known substance)*1000 = amount of moles in the substance

3rd Step) (amount of moles in substace/volume of unknown substance)*1000 = concentration of unknown substance

EXAMPLE

0.1mol/dm3 26.3cm3 of HCl added to ?mol/dm3 25cm3 of NaOH

1st step) HCl + NaOH -> NaCl + H2O

2nd) (0.1/26.3)*1000=0.00263 moles

3rd) (0.00263/25)*1000= 0.1052

Therefore the answer is 1052mol/dm3 of NaOH

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