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Chemistry A- Level > CH4: Inorganic Chemistry + Periodic Table > Flashcards

CH4: Inorganic Chemistry + Periodic Table Flashcards

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1
Q

Trend of ionisation energy down group 2? How does this explain the reactivity trend down the group?

A

DECREASES:
Extra inner shells shield outer electrons from attraction to nucleus
- also larger atomic radius down the group —> less electrostatic attraction to nucleus

The higher the first/second ionisation energies - need more energy to lose an electron - so *less likely to lose electron —> less reactive
Ionisation energy decreases, reactivity increases

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2
Q

Group 2 reactions with water, oxygen ad chlorine ?

A

WATER : M + 2H20 —> M(OH)2 + H2
Metal hydroxide and hydrogen (beryllium oxide doesn’t react with water)
OXYGEN : 2M +O2 —> 2MO
Form oxides
CHLORINE : M + Cl2 —> MCl2
Form chlorides

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3
Q

Magnesium’s reactions with water?

A

Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)
- reacts extremely slowly in cold water (mg hydroxide and hydrogen)
- Solution formed is weakly alkaline (pH 9-10) as magnesium hydroxide is only slightly soluble
- magnesium is heated in steam, forms magnesium oxide and hydrogen gas:
Mg (s) + H2O (g) → MgO (s) + H2 (g)

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4
Q

Why do the oxides form more strongly alkaline solutions down the group ?

A

Hydroxides get more soluble

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5
Q

Group 2 oxides reaction with dilute acid?

A

MO + 2HCl —> MCl2 + H2O
Reaction with HCl : forms chloride + water
Reaction with sulphuric acid : forms sulfate + water

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6
Q

Hydroxide reactions with water and dilute acid?

A

M(OH)2 (s)+ H2O —-> M(OH)2 (aq)

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7
Q

Solubility trends of group 2?

A

Compounds of group 2 elements that contain single charged negative ions (OH-) INCREASE in solubility down the group - ALSO INCREASES ALKALINITY
Compounds with double charged negative ions (SO4 2-) decrease in solubility down the group

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8
Q

What is thermal decomposition?

A

the breakdown of a compound into two or more different substances using heat

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9
Q

What do group 1/2 carbonates decompose into?

A

GROUP 1 : thermally stable , so Bunsen can’t make them decompose (EXCEPT LITHIUM CARBONATE —> forms lithium oxide/co2 )
GROUP 2 : Metal oxide and carbon dioxide gas

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10
Q

How do group 1/2 nitrates decompose ?

A

GROUP 1 : Decompose to form metal NITRITE (NO2 -) /oxygen
Except lithium nitrate : forms nitrogen dioxide , lithium oxide and oxygen

GROUP 2: forms oxide, nitrogen dioxide (toxic), and oxygen

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11
Q

Why does the thermal stability of group 1/2 increase down the groups?

A

Cation ( + ions) POLARISE the anions (- ions - nitrate /carbonate ions) , distorting it
The greater the distortion , the less stable it is

LARGER CATIONS CAUSE LESS DISTORTION THAN SMALLER CATIONS, bc they have lower charge density
- down the group, cations are larger, so less charge density and less distortion caused —> MORE STABLE

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12
Q

Why are group 2 compounds less thermally stable than group 1 compounds?

A

Group 2 have 2+ charge

The greater the charge on the cation, greater the distortion, so anions become less stable

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13
Q

How to carry out flame tests?

A
  1. Mix compound with HCl
  2. Heat piece of platinum/Nichrome wire in hot Bunsen flame
  3. Dip wire into compound/acid mixture /hold in flame
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14
Q

Flame colours of group1/2 metals?
Li , Na, K, Rb, Cs, Ca, Sr, Ba

A

Li - red
Na- orange/yellow
K - lilac
Rb - red
Cs - blue
Ca- brick red
Sr- crimson
Ba - green

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15
Q

What causes the flame colours ?

A

As electron falls back down to lower energy levels, they release energy in form of light
- the difference in energy between the higher/lower levels determines the wavelength of light released

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16
Q

Halogen colours down the group?
F,cl, br,i

A

F2 - pale yellow gas
Cl2 - green/yellow gas
Br2 - orange /brown liquid
I2 - grey/black solid , purple vapour

17
Q

Why do Mp/Bp increase down group 7?

A

Increase in electron shells down the group, STRONGER LONDON FORCES
- harder to overcome, so higher MP/BP

As MP/BP increase down the group, the volatility decreases
- it iS more volatile if its easier to evaporate (lower BP)

18
Q

Trend in electronegativity down group 7 ?

A

How strongly atoms attracts electrons to itself in a covalent bond
ELECTRONEGATIVITY DECREASES down the group as:
- atomic radii increase down group (outer shells further for nucleus ) —> less attraction to nucleus
- more shielding down the group
Harder to attract electron (oxidising power) decreased

19
Q

Why does reactivity decrease down group 7?

A

Halogens reacts by GAINING AN ELECTRON (-1 IONS)
- so has been reduced/acts an oxidising agent

As you go down group :
Atomic radii increases/shielding increases, so less attraction to nucleus —> harder to attract electrons

20
Q

How can displacement reactions show the more reactive halogen /best oxidising agent?

A

Chlorine will displace both bromine/iodine
- so is therefore REDUCED itself (gain electrons) , but acts as an oxidising agent (oxidises bromine/iodine)

21
Q

Observations when chlorine reacts with halides (potassium bromide or potassium iodide)
And what happens when organic solvent is added?

A

Chlorine + Potassium Bromide :
Solution become YELLOW - ORANGE (bromine formed)
Cl2 + 2Br - —> 2Cl- + Br2 ( Chlorine is reduced , gains electrons as it displace bromine)

IF ORGANIC SOLVENT ADDED : layer will be yellow orange

Chlorine + Potassium Iodide:
Solution becomes brown (iodine formed)
Cl2 + 2I - —> 2Cl- + I2

IF ORGANIC SOLVENT ADDED : layer will be PURPLE

22
Q

Halogen reactions with group 1/2 metals ?

A

Form ionic compounds which are halide salts
2Na + Cl2 —> 2NaCl
Na is oxidised , bc oxidation no goes from 0 to +1

SO HALOGENS ACT AS OXIDISING AGENTS

23
Q

Halogen reactions with Iron ?

A

Chlorine/bromine can oxidise iron (II) to iron (III)
However, iodine is oxidised from iodide ions when reacted with iron

24
Q

What is a disproportionate reaction?
Example of this in cold alkalis?

A

Reaction where the same species is both oxidised/reduced
Cold alkalis :
Cl2 + 2NaOH —> NaCl + NaClO + H20
Ionic equn: Cl2+ 2OH- —> Cl- + ClO-+ H20

Chlorine is oxidised(OX number goes from 0 TO +1 ) for Cl2 to ClO-
Chlorine is reduced (OX number goes from 0 to -1) for Cl2 to Cl-

25
Q

Reaction of chlorine with water/ how does it clean water?

A

CL2 + H20 —> HCl + HClO
OX NUMBERS: 0 -1
0 +1
- DISPROPORTIONATE REACTION
Chloric acid sterilises water by killing bacteria

Chloric acid can further dissociate in water to from ClO-
HClO —> H+ + ClO-
ClO- can be used as a sterilising agent

26
Q

Why does reducing power of halides increase down the group?

A

Down the group attraction to nucleus is weaker :
Atomic radius increases, more shielding

  • can lose electrons easier
27
Q

Reactions of halide ions with sulfuric acid?

A

Chloride ions:

H2SO4 (l) + NaCl (s) → HCl (g) + NaHSO4 (s)
- white fumes seen bc of HCl gas

Bromide ions:

H2SO4 (l) + NaBr (s) → HBr (g) + NaHSO4 (s)
- misty fumes from HBr gas

2HBr (g) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l)
Sulfuric acid oxides HBr TO FORM BROMINE /acid is reduced into SO2
- bromine is reddish-brown gas

Iodine ions :

H2SO4 (l) + NaI (s) → HI (g) + NaHSO4 (s)

2HI (g) + H2SO4 (l) → I2 (g) + SO2 (g) + 2H2O (l)
- sulfuric acid oxidises HI /itself is reduced to SO2
Iodine is seen as purple vapour

6HI (g) + H2SO4 (l) → 3I2 (g) + S (s) + 4H2O (l)
Sulfuric acid oxides HI again/itself is reduced to SULFUR - YELLOW SOLID

8HI (g) + H2SO4 (l) → 4I2 (g) + H2S (s) + 4H2O (l)
Sulfuric acid oxidises HI again/ itself reduced to hydrogen sulfide (H2S) - BAD EGG SMELL

28
Q

How are halide ions identified in an unknown solution?

A

Dissolving solution in NITRIC ACID + silver nitrate + ammonia
Nitric acid remove ions that interfere with reaction

React with silver nitrate like this:
Ag+ (aq) + Cl- (aq) → AgCl(s)
If halide ion present , precipitate of silver halide formed (AgX)

Reacting silver halide solution with ammonia :
If precipitate dissolves in diluteammonia —> CHLORIDE
If precipitate doesn’t dissolve in dilute ammonia, but in concentrated—> BROMIDE
If precipitate doesn’t dissolve in either —> IODIDE

29
Q

Colour of silver halide solution if it contains : Cl-, Br-, I-

A

Cl- : white
Br- : cream
I- : pale yellow

30
Q

Reaction of hydrogen with halides?

A

Forms hydrogen halide (e.g hydrogen chloride)

1) Hydrogen halides react with ammonia gas to from AMMONIUM HALIDES

2) Hydrogen halides react with water :
Hydrogen chloride + water —> Hydrochloric acid

31
Q

Test for sulfate ions?

A

Add dilute HCl and barium chloride solution
- white precipitate forms if sulfate present

32
Q

Test for ammonium compounds?

A

If ammonia is present , turns red litmus paper, blue

33
Q

Devise a procedure to identify the nitrates if lithium,rubidium and strontium using heat /any precipitation reactions of the compounds? (6)

A
  • no brown gas on heating RbNO3 (group 1 so doesn’t produce nitrogen dioxide)
  • brown gas on heating LiNO3 and Sr(NO3)2
    Dissolveall
  • add H2SO4
  • white precipitate for Sr(NO3)2 - solubility of group 2 sulfate decrease down the group so sulfate ions stay as precipitate
  • no precipitate for LiNO3 or RbNO3 - group 1 compounds soluble in water

Chemistry A- Level (20 decks)

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