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AS Chemistry > 4 - Inorganic Chemistry & The Periodic Table > Flashcards

4 - Inorganic Chemistry & The Periodic Table Flashcards

1
Q

What are the trends in group 2 for:

  • Atomic radius?
  • First ionisation energy?
  • Electronegativity?
  • Melting points?
A
  • Atomic radius: increases down group due to more energy levels. Greater distance/shielding effect offsets nuclear charge effect
  • 1st IE: decreases down group due to increased distance/shielding allowing electrons to be lost more easily
  • Electronegativity: decreases down group as atoms soon become too large to form covalent bonds, forming ionic instead
  • MPs: decrease down group due to weaker metallic bonding
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2
Q

What is the reaction of the group 2 metals with water?

A

Produces metal hydroxide + hydrogen

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3
Q

Why is Beryllium so unreactive?

A

Has a strong resistant layer of oxide on its surface, breaking only above 750°C to reveal the metal beneath

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4
Q

What are Magnesium’s reactions with steam and cold water?

A
  • Steam: produces white MgO + H2

* Cold water: reacts slowly to form Mg(OH)2 + H2. Reaction stops immediately as the hydroxide is practically insoluble.

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5
Q

How do Ca, Sr and Ba react with cold water?

A

Quickly form white metal hydroxide and bubbles of hydrogen gas

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6
Q

What is the trend in reactivity for group 2?

A

More reactive as you go down the group

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7
Q

What effect does group 2’s reactivity have on the formation of precipitates in reactions with water?

A

Less precipitate formed as you go down the group as the hydroxide becomes increasingly soluble.

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8
Q

What is the reaction of group 2 with oxygen?

A

Produce solid white oxides (metal is oxidised, losing 2e-)

• Be only reacts in the form of powder.

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9
Q

What are the flame colours of group 2?

A
  • Mg: white
  • Ca: brick red
  • Sr: red
  • Ba: pale apple green 🍏
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10
Q

How do Sr and Ba react with oxygen and why?

A

Form peroxides (MO2). Sr & Ba have low polarising power and are not able to break the peroxide ions down to the metal oxide and oxygen.

Reactions with air produce mixture of metal oxide and -nitride

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11
Q

What is the reaction of Group 2 with Chlorine?

A

Produce solid white chlorides, soluble and dissolve to form hydrated cations.

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12
Q

What is the reaction of group 2 oxides with water?

A

Form soluble metal hydroxides which are strongly alkaline due to OH- ion.
> MgO reacts slowly and isn’t very soluble
> BeO doesn’t react
> CaO, SrO, BaO react exothermically to produce increasingly alkaline solutions.

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13
Q

What is the reaction of group 2 oxides/hydroxides with acids?

A

Produce salt and water in a neutralisation reaction.

> BeO is amphoteric (reacts as acid AND base), and so forms oxy-anions Be(OH)4 2-

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14
Q

What is the reaction of Ca(OH)2 with limewater and carbon dioxide?

A

Produces salt + carbonate + water. CO2 turns limewater cloudy as a test to show for its presence.

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15
Q

What are the trends in solubility regarding group 2?

A
  • Singly charged ions INCREASE in solubility down group
  • Doubly charged DECREASE
  • Hydroxides INCREASE
  • Sulphates DECREASE (BaSO4 is insoluble)

• Mg(OH)2 has low solubility (sparingly soluble)

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16
Q

What can barium sulphate be used for and why?

A

‘Barium meals’ are ingested before X Rays, the X Ray tracing it through the digestive system (appearing as opaque due to high nuclear charge).

Able to do this as it is so insoluble that it can pass through the alimentary canal without dissolving.

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17
Q

How do you test for sulphate ions?

A
  1. ) Add HCl to sample
  2. ) Add NO3 or BaCl2
  3. ) If sulphate ions are present, a white precipitate of BaSO4 is formed.
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18
Q

What is thermal composition and what is its trend down group 2?

A

The heat needed to break down a substance - the more thermally stable the substance, the more heat required for decomposition.
• Decreases down g2.

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19
Q

What is thermal stability dependent upon and what is its trend down G2?

A

The cation’s polarising power (determined by the charge density)
-> larger charge and smaller radius result in greater charge density.
• Increases down G2

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20
Q

What is polarisation and what are its trends down G2?

A

Causes the cation to distort the anion as it attracts the anion’s electrons.
• Decreases down G2 due to larger ionic radii and lower charge density
• Increases across periods due to increasing charge

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21
Q

What happens during the thermal decomposition of G1 carbonates?

A

NOTHING - G1 has such high thermal stability, large radii and weak polarising power that they do not thermally decompose.

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22
Q

What is the exception to the trend in G1 carbonate thermal decomposition and why is this?

A

Lithium carbonate: decomposes like G2 to form Li2O and CO2. This is because it has a very small cation and is sufficiently polarising enough to break the O-C bond in the CO3 2- ion to form O 2-

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23
Q

What happens during the thermal decomposition of G2 carbonates and what is the trend for this?

A
  • Form metal oxide and oxygen
  • Except for barium carbonate, which only decomposes under severe heat as it is so thermally stable.
  • Ease of thermal decomposition DECREASES down group due to increased thermal stability
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24
Q

What happens during the thermal decomposition of G1 nitrates (except for LiNO3)?

A

Decompose to form metal nitrite (2MNO2) and oxygen

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25
Q

What happens during the thermal decomposition of lithium nitrate and why?

A

Forms 2Li2O + 4NO2 + O2

Due to Li’s small ionic radius and high charge density giving it enough polarisation power to polarise O-N bonds in NO3 to form O 2-.

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26
Q

What happens during the thermal decomposition of G2 nitrates?

A

Form metal oxide, brown NO2 and oxygen gas.

• Lowest temp for Be, highest for Ba.

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27
Q

What experiment can be undertaken to investigate thermal decomposition of carbonates?

A

Heat specific number of miles of different carbonates and time how long it takes for limewater to go cloudy due to production of CO2.
• Faster = easier decomposition

28
Q

What experiment can be done to investigate the thermal decomposition of nitrates?

A
  • Test for oxygen by putting glowing splint near reaction - if oxygen is present, it will relight.
  • In fume cupboard, time how long it takes for a certain amount of brown NO2 gas to form.
29
Q

What is the method for a flame test?

A
  1. ) Dip compound in HCl
  2. ) Heat nichrome wire in flame to ensure it is clean
  3. ) Dip wire into compound/HCl mixture
  4. ) Observe flame colour
30
Q

What are the flame colours for G1?

A
  • Li - crimson
  • Na - orangey yellow
  • K - lilac
  • Rb - red
  • Cs - blue
31
Q

What are the trends for the halogens in:

  • Atomic radius?
  • Electronegativity?
  • First electron affinity?
  • First ionisation energy?
  • Melting and boiling points?
A
  • Radius: INCREASES down group as more energy levels
  • Electro: DECREASES down group as larger radii - less attraction from nucleus to electrons
  • Affinity: DECREASES down group (except F) due to larger radii meaning electron further from nucleus
  • IE: DECREASES down group as increased distance/shielding effect; more energy levels
  • MPs/BPs: INCREASE down group as increased london forces due to more energy levels (as all molecules diatomic)
32
Q

Why does Fluorine have a lower first electron affinity than does Chlorine?

A

Incoming electron repelled by existing electrons, decreasing effect of nuclear attraction and lowering electron affinity despite F being smaller than Cl.

33
Q

What is the solubility of G7?

A

• Cl, Br and I dissolve in organic solvents but with no pattern: dissolve only in organic as this contains London forces; the attractions broken are similar to those formed.

34
Q

What is the trend in reactivity for the halogens and why?

A

DECREASES down group as larger Atomic radii mean greater distance/shielding effect, making it harder for the nucleus to attract the incoming electrons it requires in order to react.

35
Q

What are the physical properties of the halogens?

A 
(All non-polar covalently-bonded diatomic molecules)
• F2: pale yellow gas 
• Cl2: green gas 
• Br2: red-brown liquid
• I2: grey solid
36
Q

What colour do Cl, Br and I go when dissolved in:

  • water?
  • organic compounds such as C6H14?
A

WATER:
• Cl: colourless
• Br: yellow-orange
• I: brown

ORGANIC:
• Cl: colourless
• Br: orangey red
• I: pinky violet

37
Q

How do halogens react in reactions with other halogen solutions and why?

A

Displacement redox reactions occur, halogens displacing only any elements LOWER than them in the group (e.g. F displaces Cl/Br/I, Cl displaces Br/I…)

• this happens because of the decreasing strength of halogens as oxidising agents.

38
Q

What colour changes can be seen when Cl, Br and I react with:

  • KCl?
  • KBr?
  • KI?
A 
• Cl
- KCl: no reaction 
- KBr: no colour change
- KI: no colour change
• Br
- KCl: goes orangey brown
- KBr: no reaction 
- KI: no colour change
• I
- KCl: goes dark brown
- KBr: goes dark brown
- KI: no reaction
39
Q

How do the halogens react with G1 & 2 metals?

A

Form ionic halides with both G1 and G2 metals, oxidising the metal and reducing the halogen.

40
Q

How do the halogens individually react with Iron?

A
  • F: cold iron wool burns in cold F to give FeF3 (white/pale green)
  • Cl: in gas form over hot iron to form FeCl3 (anhydrous black crystals or reddish-brown if water impurities)
  • Br: gas over hot iron, less vigorously than Cl forms anhydrous FeBr3 (reddish brown solid)
  • I: less vigorous, forms grey FeI2
41
Q

Why do the different halogens react differently with iron?

A

Iron has variable valency and so reacts differently with halogens of different strengths of oxidising agents. Iodine is the weakest oxidising agent and so only iron (II) iodide is formed instead of iron (III).

42
Q

How do the halogens react with water?

A 
Iodine and Fluorine do not react, but Cl and Br do:
Cl2 + H2O = HCl + HClO
Br2 + H2O = HBr + HOBr
 BOTH DISPROPORTIONATION
(= is equilibrium)
43
Q

How is Chlorine used to treat water?

A

HClO + H2O = ClO- + H3O+

The chlorate ions in ClO- kill bacteria to make water drinkable. Some Cl remains in the solution to continue to kill harmful bacteria.

44
Q

How do the halogens react with cold sodium hydroxide?

A

X2 + 2NaOH -> NaOX + NaX + H2O
All halogens react to form halide + halate (I) salts in a disproportionation reaction.

• Chlorine is disproportionate further if heated to form chlorate (V) ions:
3ClO- -> 2Cl- + ClO3-

45
Q

How do the halogens react with hot sodium hydroxide?

A

3X2 + 6NaOH -> NaXO3 + 5NaX + 3H2O

Disproportionation

46
Q

How is bleach formed?

A

Through the disproportionation of Chlorine and cold sodium hydroxide, forming NaClO.

Bleach is used in water treatment and cleaning.

47
Q

How do halogens react with phosphorus when there is a limited amount of the halogen?

A

Form phosphorus trihalide (PX3), this then reacting with more halogen to form phosphorus pentahalide. (PX5)

48
Q

How do halogens react with phosphorus when there is excess halogen?

A

Form phosphorus pentahalide (PX5)

49
Q

How does iodine react with red phosphorus?

A

• Forms phosphorus triiodide (PI3)

50
Q

How is gaseous hydrogen iodide prepared?

A

Iodide reacts with red phosphorus to form PI3 and if this is damp it reacts with water to form hydrogen iodide:

PI3 + 3H2O -> 3HI + H3PO3

51
Q

How do halide ions react and what is the trend in their strength down the group?

A

Halide ions act as reducing agents (losing electron).

Strength of reducing agent INCREASES down group as Atomic radius increases (greater distance/shielding effect)

52
Q

How do KF and KCl react with concentrated sulphuric acid?

A

Form KHSO4 + HF/Cl (misty fumes of gas turn damp blue litmus red).
• when concentrated ammonia is placed near, white fumes of ammonium fluoride/chloride are visible.
• no further reaction as both F and Cl are weak reducing agents.

53
Q

What is the reaction of KBr with concentrated sulphuric acid?

A
  1. ) KBr + H2SO4 -> KHSO4 + HBr
  2. ) 2HBr + H2SO4 -> Br2 + SO2 + 2H2O (redox)
  • misty fumes of HBr turn damp blue litmus red
  • conc. ammonia forms white fumes
  • HBr is a strong reducing agent, forming colourless SO2 and orange Br2 fumes
54
Q

How does KI react with concentrated sulphuric acid?

A
  1. ) KI + H2SO4 -> KHSO4 + HI
  2. ) 2HI + H2SO4 -> I2 + SO2 + 2H2O
  3. ) 6HI + 3O2 -> 3I + H2S + 2H2O
  • misty fumes HI turn damp blue litmus red
  • white fumes with concentrated ammonia
  • HI very strong reducing agent, forming purple fumes of Iodine with H2SO4
  • HI reacts further with O2 to form more purple iodine and colourless H2S, which is toxic and smelling of rotten eggs. May also observe solid yellow sulphur.
55
Q

How do the hydrogen halides react with water?

A

HX + H2O -> H3O+ + HCl-

H-X covalent bond broken by H2O in endothermic reaction, energy regained through dative binding in H3O+

56
Q

Which of the hydrogen halides is the strongest acid and why?

A

HI because it has the weakest bonds

57
Q

How do hydrogen halides react with gaseous ammonia?

A

Form white fumes

58
Q

What is the test for halides?

A
  1. ) Add dilute nitric acid
  2. ) Add silver nitrate and observe colour:
    - F forms no precipitate
    - Cl forms white precipitate
    - Br forms cream
    - I forms pale yellow
59
Q

How can you further tell the precipitates of silver halide apart?

A

Add dilute and then conc ammonia:
• AgCl: dissolves in dilute to give colourless solution
• AgBr: unchanged in dilute but dissolves in conc to colourless
• AgI: doesn’t dissolve in either

60
Q

Why is nitric acid added to halides in the halide test?

A

Acidifies solution and prevents precipitation of other ions in the silver nitrate by the Ag+ ion

61
Q

How can you test for carbonate ions?

A

Add dilute HCl - if carbonate/hydrogen carbonate, it will produce CO2 which turns limewater cloudy

62
Q

How do you test for ammonia compounds?

A
  1. ) Add NaOH to solution
  2. ) heat gently
  3. ) hold damp red litmus paper over test tube - turns blue of ammonia present
63
Q

What hazards surround the ammonia test and how can these be avoided?

A

NH3 is irritant and may damage lungs - do in fume cupboard

64
Q

How do you test for G1/2 ions?

A

Flame test

65
Q

What is a simple test for Cl, Br and I?

A
  • Cl: turns KBr orange
  • Br: goes red/brown with excess KI
  • I: turns starch dark blue

AS Chemistry (5 decks)

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