Notes on As Chemistry Unit 1

These helped me remember all the little bits of information about the reactions and symbols, I hope someone else finds them useful

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Chemistry Notes
Mole Calculations
Solids
Amount (mol)= Mass (g) / Mr
Solutions
Amount (mol) = Volume (dm3) x concentration (mol dm -3)
Amount (mol) = [Volume (cm3)/1000] x concentration (mol dm-3)
Gases
Amount (mol) = Volume (dm3) /24
Amount (mol) = Volume (cm3) / 24 000
Formulaes
Acid Formula
HCL HCl
Sulfuric H2SO4
Nitic HNO3
Base Formula
Sodium Hydroxide NaOH
Potassium Hydroxide KOH
Ammonia NH3
Reactions of Acids
Acid + Carbonate -> Salt + Carbon dioxide + Water
Acid + Base/Alkali -> Salt + Water
Reactive Metal + Acid -> Salt + Hydrogen
Oxidation Number
Type Oxidation Numer
Uncombined Element 0
Combined Element -2
Combined Hydrogen +1
Simple Ion The Charge on Ion
Combined Fluorine -1
Systematic Names ­ Oxidation Number shown in brackets e.g Sulfate (IV) = SO3-2 ox no. = 4

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Ionisation Energy
Talk about ­ Atomic Radius, Nuclear Charge & Electron Shielding
Across Period = generally increases, increase in nuclear charge, more attraction between nucleus &
outer electrons therefore more difficult to remove electrons. Outer electrons across period in same
shell so atomic radius & shielding remain similar
Down Group ­ Decreases, electron shielding & atomic radius increase which outweigh effects of
increasing nuclear charge. So electrons get lost more easily.…read more

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Water molecules are held apart
and form lattice in which there is a lot of space
Trends across a Period
Trend Explanation
Atomic Radius ­ Decreases Electrons added to same shell, so similar
shielding, but gains protons which adds more pull
on outer electron pulling it closer to nucleus
Melting Points ­ Increase then Decrease High for metals as strong electrostatic bonding
and increase across period as number of
electrons increases and charge on ions
decreases so attraction is stronger
Covalent Bonds very strong &…read more

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Magnesium Hydroxide (Mg(OH)2) used in antacids/indigestion medication.…read more

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Cl2(g) + 2NaOH(aq) -> NaCl(aq) + NaOCl(aq) + H2O(l)
Cl is both oxidised & reduced = Disproportionation reaction
Purifying Water
Cl2(g) + H2O(l) -> HCl(aq) + HClO(aq)
Also Disproportionation reaction
Kills bacteria & safe to drink
Halide ion test
1. Add nitric acid
2. Add silver nitrate solution & see what precipitation is formed
-silver chloride is white: Ag+(aq) + Cl-(aq) -> AgCl(s)
-silver bromide is cream: Ag+(aq) + Br-(aq) -> AgBr(s)
-silver iodide is yellow: Ag+(aq) + I-(aq) -> AgI(s)
3.…read more

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