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Chemistry A Level > General > Flashcards

General Flashcards

1
Q

What is an electron density map?

A

X ray diffraction from ionic solids

Remember: the cation can distort the electron field of the anion

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2
Q

What does ionic bond strength depend on?

A

Charge density

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3
Q

What does charge density depend on?

A
  • charge of jon

* radius of ion

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4
Q

Evidence for ions

A
  • high melting and boiling point -> presence of bonds
  • conduct -> charged particles that are free to move
  • ion migration in electrolysis
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5
Q

Sigma bond

A

Lies symmetrically along an axis joining two nuclei

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6
Q

Pi bind

A

Forms alongside the atoms

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7
Q

Electron density of covalent substances

A

Even

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8
Q

Expanding the octet

A

And atom splits a pair
Takes energy
Enough energy is paid off in the making of the bond
2nd period do not do it

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9
Q

What changes the shapes of ions?

A

Electron fields move to minimise repulsion

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10
Q

Electronegatibity

A

The ability of an atom to attract the shared pair of electrons

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11
Q

Polarisation

A

Distortion of the electron regions due to different electro negativities

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12
Q

What happens when a substance has a polar bond

A

Gives covalent structures ionic qualities

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13
Q

How to decide whether a molecule is polar

A

Look at the charge centres

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14
Q

Polar molecule

A

Has partial charges

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15
Q

Dipole

A

Separation of partial charges

Causes dipole-dipole attractions

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16
Q

Evidence for London forces

A

When noble gases are fooled enough the fondnesne

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17
Q

How do LONDON forces arise

A

Electron imbalance

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18
Q

Hydrogen bindings

A

Leaves the hydrogen proton exposed Lone pair attracted to it

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19
Q

Boiling points of allâmes

A

Increase with molecular mass

Branching causes decrease

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20
Q

Hydration of Ito s

A

Water molecules linkig

Vibrating water molecules shake the ions free from the lattice

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21
Q

Bent

A
  • 2 bonding pairs
  • 1 lone pair
  • bond angle less that 120

Or
• 2
• 2
• 104.5

22
Q

Tetrahedral

A

• 4 bonding
• 0 lone
•
109.5

23
Q

Trigonal pyramidal

A
  • 3 bonding
  • 1 lone
  • 107.5
24
Q

Trigonal bipyramindal

A

• 5
• 0
• 120
90

25
Q

Octahedral

A
  • 6
  • 0
  • 90
26
Q

Barium combustion

A

Green flame

Perioxide (BaO2)

27
Q

Group 2 reactivity

A

Less reactive with water than corresponding group 1

Beryllium does not react with stream

28
Q

Metal oxide + water

A

Metal hydroxide

Except beryllium oxide

29
Q

Sulfate solubilité

A

Decreases down the group

30
Q

Hydroxide solubility

A

More soluble down the group

Calcium carbonate much less soluble than calcium hydroxide

31
Q

Carbonate decomposition

A

All group 1 do it at skl

Thermal stability increases down the group

32
Q

Explanation of carbonate

A
  • greater charge density in cation
  • greater distortion on anion
  • draws oxygen towards it, weakens C-O bind
  • vibrational energy breaks bond
  • as cations get larger, polarising power decrease
  • group 1 less than group 2
33
Q

Nitrate decomposition

A

All do it
Group 1 except Li -> metal nitrite + oxygen
Li + group 2, more polarisaient -> metal oxide + nitrogen dioxide + oxygen

34
Q

Nitrite

A

NO2-

35
Q

Flame colours

A

Calcium brick red
Strontium crimson
Barium green

36
Q

Halogens as oxidising agent

A

Chlorine is strongest
Iodine is weakest

Because chlorine takes up electrons the most easily

37
Q

Halogen + sodium

A

Burn vigorously in chlorine

React with others but less exothermic

38
Q

Chlorine + hydrogen

A

Explodes in the presence of sunlight

39
Q

Chlorine + water ->

A

HOCl + HCl

40
Q

Chlorine + cold soidym hydroxide ->

A

NaOCl + NaCl

41
Q

Chlorine + hot sodium hydroxide ->

A

NaClO3 + 5NaCl

42
Q

Chlorine water + iron(II) solution

A

Goes from green to yellow
Solution of Fe3+ is formed

Cl2 + 2Fe2+ -> 2Cl- + 2Fe3+

Bromine can, idoine can’t

43
Q

Potassium halide + concentrated sulphuric acid

A

• hydrogen halide + other substance

44
Q

KCl + H2SO4 ->

A

HCl
KHSO4 - steamy white fumes

Chlorine not strong enough reducing agent to react further

45
Q

Describe concentrated sulfur if acid

A

Oxidising agent

46
Q

Bromide + conc H2SO4

A

Orange steamy fumes

-> Br2 + 2H2O + SO2

47
Q

Iodide + conc H2SO4

A

Sulfur dioxide, iodine, hydrogen sulfure

48
Q

Reducing agent

A

Chlorine is weakest
Iodine is stronger
Gives away its outer electron most easily

49
Q

Hydrogen halides

A

Soluble
Dissociate in water
Forms acidic solution

50
Q

Ammonia + hydrogen halide

A

Dense white smoke of ammonium halide is produced

51
Q

What happens when a bond forms?

A

One electron from each atom enters a cloud of lower energy

52
Q

Average bond enthalp

A

Calculated in the gaseous state

Innacfutaye because environment affects bond

Chemistry A Level (12 decks)

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