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Chemistry > Topic 4 - Inorganic Chemistry > Flashcards

Topic 4 - Inorganic Chemistry Flashcards

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1
Q

Trend in Ionisation Energy down group 2

A

Ionisation energy decreases down group 2
This is because both the atomic radius and shielding increases which means there is greater distance between the positive nucleus and the negative outer electrons and therefore there are weaker forces of electrostatic attraction. The increase in the number of protons and therefore the nuclear charge is overriden by the effect of shielding

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2
Q

Trend in reactivity down Group 2

A

Reactivity increases since ionisation energy decreases due to increase in atomic structure and shielding. Therefore less energy is required to break the electrostatic forces of attraction between the positively charged nucleus and the negatively charged outer electron

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3
Q

Group 2 + Water

A

React to form metal hydroxides/bases
Reactivity increases down the group (no reaction with Be)
Mg reacts slowly with cold water but vigorously with steam and produced MgO instead of a hydroxide

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4
Q

Group 2 + Oxygen

A

React to form metal oxides/bases
Redox reaction - oxygen is reduced and metal is oxidised
Group 2 oxides are white solids

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5
Q

Group 2 + Chlorine

A

React to form metal chlorides
Redox reaction - chlorine is reduced and metal is oxidised

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6
Q

Group 2 oxides + Water

A

Form bases and alkaline solutions
–> Oxides react readily with water to form hydroxides which dissociate to form OH- ions (except for Be which will not react with water)

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7
Q

Group 2 oxides / hydroxides + Dilute Acid

A

Both Group 2 oxides and hydroxides are bases and therefore can neutralise acids
acid + base –> salt + water

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8
Q

Trend in solubility of Group 2 Sulfates

A

Sulfates are -2 charged and therefore decrease in solubility as you go down the group

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9
Q

Trend in solubility of Group 2 Hydroxides

A

Hydroxides are -1 charged and therefore increase in solubility as you go down the group

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10
Q

Trend in thermal stability of nitrates and carbonates of elements in group 2 in terms of size and charge of cations

A

Group 2 carbonates and nitrates can decompose upon heating

  • Carbonates break down into metal oxides and carbon dioxide (via thermal decomposition)
  • nitrates break down into metal oxides, nitrogen dioxide and oxygen (via thermal decomposition)

Both carbonates and nitrates become more thermally stable as you gown down the group

Carbonate and nitrate ions have a large electron cloud that can be distorted when nearby +group2 ions - as you go down the group, the group 2 metals become larger in size and therefore their charge is spread out over a larger area and they have a lower charge density and therefore they distort the carbonate/nitrate less

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11
Q

Trend in thermal stability of nitrates and carbonates of elements in group 1 in terms of size and charge of cations

A

Group 1 Carbonates are thermally stable under a bunsen flame (except for Lithium carbonate which will form an oxide and carbon dioxide)

Group 1 Nitrates break down into nitrates and oxygen upon heating (except LiNO3 which decomposes to form Li2O, NO2 and O2)

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12
Q

Testing Thermal Decomposition of Group 1 and 2 Nitrates

A

Nitrates (NO3-)
- We can measure how long it takes a specific amount of oxygen to be produced. Using a gas syringe or the amount needed to relight a glowing splint
- The length of time it takes until a specific amount of NO2 is produced (brown gas - can easily be observed, but is toxic so must be done in a fume cupboard)

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13
Q

Testing Thermal Decomposition of Group 1 and 2 Carbonates

A

Carbonates (CO32-)
- The length of time it takes until a specific amount of CO2 is produced - CO2 turns limewater cloudy so the quicker this turns cloudy, the more CO2 produced - could use a gas syringe

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14
Q

Flame colours in compounds of Group 1 and 2 element

A

Test for positive ions / cations

We get different colours because electrons in shells move to higher energy levels as they absorb energy from the flame. When they drop back to lower energy levels, light is released. Different colours are produced as the difference in energy levels determines the wavelength of light released

  1. Dip the nichrome wire in HCL
  2. Dip in sample
  3. Place loop into blue bunsen flame and observe flame

Crimson - Li+
Yellow/Orange - Na+
Lilac - K+
Red - Rb+
Blue - Cs+

Dark red - Ca2+
Crimson - Sr2+
Green - Ba2+

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15
Q

Halogens - Group 7 elements

A

Fluorine - pale yellow gas
Chlorine - pale green gas
Bromine - Brown/Orange liquid
Iodine - grey solid

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16
Q

Boiling Point of Group 7

A

Boiling point increases down the group - this is because the London forces increases due to increasing size and relative mass of atoms - therefore physical state goes from gas at top of group to solid at bottom

17
Q

Electronegativity Trend group 7

A

Electronegativity is the ability for an atom to attract a bonding pair of electrons in a covalent bond

Electronegativity decreases down the group - because the atoms get larger (atomic radius increases and shielding increases) therefore the distance between the positive nucleus and bonding electrons increase + there is also more shielding

18
Q

Reactivity of Group 7 elements

A

Reactivity of the halogens decreases down the group

This is because there is an increase in atomic mass and electron shells - so the atoms are larger as you go down the group. Therefore, the attraction of the outer electron to the nucleus decreases

19
Q

Displacement reactions between halogens and halide ions in aqueous solution, followed by addition of organic solvent

A

A more reactive halogen will displace a less reactive halide ion
- Reactivity of halogens decrease down the group - atomic radius is smaller so attracts electrons better than larger atoms
- Halogens also less oxidising as we go down the group
- Halogen will displace a halide from solution if the halide is lower in the periodic table

20
Q

Displacement reactions between halogens and halide ions in aqueous solution, followed by addition of organic solvent

A

Adding an organic solvent (hexane) to halogens can make it easier to observer colour changes

  • The halogen present will dissolve readily in the organic solvent
  • Forms a layer above the aqueous layer and a coloured band will appear
21
Q

What are the actual reactions between halide ions and halogens

A

Chlorine water + Potassium chloride (NO REACTION)
Chlorine water + Potassium bromide
(yellow aqueous layer and orange organic layer)
Cl2 + 2Br- –> 2Cl- + Br2
Chlorine water + Potassium iodide
(brown aqueous layer and purple organic layer)
Cl2 + 2I- –> 2Cl- + I2

Bromine water + Potassium chloride (NO REACTION)
Bromine water + Potassium bromide (NO REACTION)
Bromine water + Potassium iodide
(brown aqueous layer and purple organic layer)

Iodine solution + Potassium chloride (NO REACTION)
Iodine solution + Potassium bromide (NO REACTION)
Iodine solution + Potassium iodide (NO REACTION)

22
Q

colours of halogens and halide ions

A

Potassium chloride/bromide/ iodine = colourless
Chlorine water - yellow
bromine water - orange
iodine solution - brown

23
Q

Halogen + Group 1 and 2 Elements

A

Form metal halides - redox reactions
- metal is oxidised and halogen is reduced

24
Q

Halogens react with cold alkalis in disproportionation reactions

A

Disproportionation reacts are where there is a simultaneous reduction and oxidation of halogen

  • makes a salt with 1 oxygen
  • eg - sodium bromate (1)
25
Q

Halogens react with hot alkalis in disproportionation reactions

A
  • makes a salt with 3 oxygens
  • eg - sodium chlorate (V)
26
Q

Disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide

A

Mixing chlorine and sodium hydroxide will form sodium chlorate(I) solution - also known as bleach

chlorine has been simultaneously reduced and oxidised

can be used to treat water, bleaching paper and fabrics, and as a cleaning agent

27
Q

Disproportionation reaction of chlorine with water and use of chlorine in water treatment

A

Adding water to chlorine will produce chlorate(I) ions which kill bacteria - useful in drinking water and pools

chlorine has been simultaneously reduced and oxidised

Chloric(I) acid ionises to make chlorate(i) ions - hypochlorite ions

28
Q

Hydrogen halides

A

Gases that dissolve in water to form acidic solutions
- hydrochloric acid / hydrobromic acid / hydroiodic acid

React with water in air to form white misty fumes
React with ammonia gas to make white fumes of ammonium halides

28
Q

Reducing ability of of hydrogen halides increases down the group
- solid group 1 halides with concentrated sulfuric acid

A

Halide ions lose an electron in reactions and so are good reducing agents

  1. Reactions with sulfuric acid
    - Some halide ions can reduce sulfuric acid
    NaCl + H2SO4 –> NaHSO4 + HCi (white misty fumes)
    NaBr + H2SO4 –> NaHSO4 + HBr (orange vapour) - Br- ions oxidised and S reduced
    NaI + H2SO4 –> NaHSO4 + HI (yellow solid of S produced) - I- ions oxidised and S reduced - can further reduced S into H2S - I- ions oxidised and S reduced (again) - evident via rotten egg smell
  2. Reaction with silver nitrate (and confirm with ammonia solution)
    - add dilute nitric acid then silver nitrate solution - colour of precipitate allows you to identify the halide ion -
    - we add nitric acid to react with any anions other halides - could give a false result

Chloride ions (white precipitate - silver chloride)
Bromide ions (cream precipitate - silver bromide)
Iodide ions (yellow precipitate - silver iodide)

  • to distinguish if colours look similar, add ammonia solution to the precipitates
    Cl- white precipitate will dissolve in dilute
    Br- cream precipitate dissolves in concentrated
    1- yellow precipitate insoluble in concentrated
  • Both prove the trend
  • radius increases down the group and therefore distance between nucleus and outer electron is larger so attractive forces are weaker which means outer electron is lost more readily and so reactivity increases down the group
29
Q

Test for ions

A

Test for carbonates
- Add acid to carbonate
- From hydrogencarbonates and CO2
- test to see if CO2 is present by pushing through limewater which will turn it cloudy

Test for Sulfates
- add HCL to remove any carbonates (no false positives)
- Then add barium chloride
- white precipitate will form (barium sulfate) - insoluble

30
Q

Test for ions

A

Test for Ammonium compounds
- Add sodium hydroxide and gently heat - ammonia gas will be produced
- Use damp red litmus paper which will turn blue

Test for hydroxides
- Alkaline so red litmus paper blue - doesn’t say its hydroxide
- Spectroscopy - further tests to identify alkali (OH-)

Chemistry (7 decks)

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