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Chemistry Notes

Mole Calculations


Amount (mol)= Mass (g) / Mr


Amount (mol) = Volume (dm3) x concentration (mol dm -3)
Amount (mol) = [Volume (cm3)/1000] x concentration (mol dm-3)


Amount (mol) = Volume (dm3) /24
Amount (mol) = Volume (cm3) / 24 000


Acid Formula

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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…

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oxygen atom. 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…

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Magnesium Hydroxide (Mg(OH)2) used in antacids/indigestion medication. Weak alkali ­ neutralises
excess stomach acid Mg(OH)2 + 2HCl -> MgCl2(aq) + 2H2O(l)

Calcium Hydroxide (Ca(OH)2), slaked lime, spread by farmers on acidic soil

Group 7

Go round in pairs


Down group elements become less volatile as Van Der Waals forces…

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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…


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