1 - Inorganic Chemistry and the Periodic Table Flashcards
Atomic Radius trend in group 2?
Increases down the group as there are more shells of electrons.
Melting Point trend in group 2?
Melting points decrease down the group as the metallic bonding is weakened by the increased atomic radius as the distance between the positive ions and the delocalised ions increases and thus the electrostatic attractive force decreases in strength.
1st Ionisation energy trend in group 2?
Decreases down the group as the outermost electrons are successively further from the nucleus and are more shielded, leading to an increase in repulsive force from the electrons.
Reactivity trend in group 2?
Increases down the group as the atomic radii increases and there is more shielding. The attraction between the outermost electron and the nucleus is therefore decreased and it is easier to remove electrons and form cations.
Group 2 reactions with oxygen?
Burn in oxygen to form metal oxides (ionic bonding)
Group 2 reactions with chlorine?
Reacts with chlorine to form metal chlorides (MgCl2)
Group 2 reactions with water?
Increasing reactivity with water down the group, creating more vigorous bubbling of H2 down the group.
Mg will burn in steam to produce MgO and H2
In warm water it will make the hydroxide product Mg(OH)2 + H2
Other group 2s will form the hydroxide and hydrogen with cold water
Observations: Fizzing, metal dissolving, Solution heating up
Group 2 ionic oxide reactions with water?
Forms hydroxides, higher pHs down the group
Reaction of group 2 ionic oxides with acids?
Produces salt and water (MgCl2 + H2O)
Reaction of group 2 hydroxides with acids?
Produces salt and water (MgCl2 + H20)
Solubility trend of group 2 hydroxides?
- Increasingly soluble down the group
- Mg is sparingly soluble, forms Mg(OH)2, white precipitate, which is milk of magnesia, used as antacid (preferable as only weakly alkaline)
- Ca(OH)2 is limewater, used to detect for CO2 or neutralise acidic soil
Solubility trend of group 2 sulphates?
- Less soluble down the group
- BaSO4 used as a contrast medium in medical x-ray photographs
Group 2 decomposition trend?
- Decomposes into metal oxide and CO2
- The ease of thermal decomposition decreases down the group and thermal stability increases down the group
- Cations become bigger and have less of polarising power and distort the carbonate ion less. The C-O bond is weakened less and breaks less easily
Group 1 decomposition trend?
Lithium is the only element to decompose as it is such a small ion that it has a polarising effect
Experiment to investigate the ease of group 2 carbonate decomposition?
Heat known mass of carbonate and pass gas through limewater. Time for the first permanent cloudiness to appear.
Thermal decomposition trend of group 2 nitrates?
- Decompose to produce group 2 oxide, oxygen and nitrogen dioxide gas. Brown gas (NO2) would be observed.
2Mg(NO3)2 –> 2MgO + 4NO2 + O2 - The ease of thermal decomposition decreases down the group and thermal stability increases down the group.
- Cations become bigger and have less of polarising power and distort the carbonate ion less. The N-O bond is weakened less and breaks less easily
Thermal decomposition trend of group 1 nitrates?
- Produces Nitrate (III) salt + Oxygen 2NaNO3 --> 2NaNO2 + O2 Sodium nitrate(V) --> Sodium nitrate(II) - Exception: Lithium nitrate decomposes the same as group 2 nitrates: 4 LiNO3 --> 2Li2O + 4NO2 + O2
Flame test method
Use a nichrome wire, clean it in concentrated hydrochloric acid and heat in the blue bunsen flame. If the sample is not solid, crush it, and dip it into sample and then into the bunsen and observe the flame.
Explanation of flame colour
Heat causes the electron to move to a higher energy level, the electron drops back down to ‘ground state’, as it falls to a lower energy level, energy is emitted in the form of visible light energy with the wavelength of the observed light.
Flame colours
Red, Yellow, Lilac, Red, Blue, No colour, Red, Red, Green
Describe the group 7 halogens
Covalent - simple molecular - diatomic F - Very pale yellow gas Cl - Greenish gas Br - Red liquid (Dense brown fumes) I - Shiny grey solid, sublimes to purple gas
Trend in melting point and boiling point for group 7?
- Increases down the group
- Molecules become larger with large atomic radius, larger London Forces between them, stronger intermolecular forces means more energy needed to break the bonds.
Trend in electronegativity for group 7?
- Decreases down the group
- Atomic radii increases and therefore the nucleus is less able to attract the bonding pair of electrons
Trend in reactivity for group 7?
- Decreases down the group
- Atoms bigger (larger atomic radii), with more shielding, less easily attract and accept electrons
Oxidation reactions of halide ions by halogens
- Strong oxidising agent halogens will displace a halogen that is a less strong oxidising agent.
- Oxidising strength decreases down the group
- Chlorine will displace both bromine and iodine, bromine will displace iodine
- The colour of the solution will show which halogen has been displaced or has not reacted
What colour will be present in a test tube with a solution of each halogen?
Cl - Very pale green solution
Br - Yellow solution
I - Brown solution
What colour will be present in a test tube with a solution of each halogen when an organic solvent is added?
Cl - Colourless
Br - Yellow/Orange
I - Purple
What is an organic solvent that can be used?
Hexane
Oxidation reactions with halogens and metals?
Metals are oxidised
3CL2(g) + 2Fe –> 2FeCl3(S)
Br2(I) + 2Na(s) –> 2NaBr(s)
Oxidation reactions with halogens and metal ions?
Chlorine and Bromine can oxidise Fe2+ to Fe3+ but Iodine is not strong enough oxidising agent for this
Cl2(g) + 2Fe2+(aq) –> 2Cl-(aq) + 2Fe3+
2I-(aq) + 2Fe3+(aq) –> I2(aq) + 2Fe2+(aq)
What is disproportionation?
The reaction where an element is simultaneously oxidised and reduced
Reaction of chlorine with water
CL2(aq) + H20(l) –> HCLO(aq) + HCL
0 -1 (reduction) +1 (oxidation)
Universal indicator will turn read due to acidity then HCLO bleaches the colour
Pale greenish solution due to chlorine (chlorine water_
Disproportionation reaction
Chlorine reaction with cold alkali
Cl2(aq) +2NaOH(aq) --> NaCl(aq) + NaClO(aq) + H20(l) Colour will fade to colourless Sodium chlorate (I) produced - bleach NaOH is dilute Disproportionation reaction
Halogen reaction with hot alkali
3Cl2(aq) + 6NaOH(aq) –> 5NaCl(aq) + NaClO3 + 3H20(l)
Concentrated NaOH
Sodium chlorate (V) produced
Disproportionation
Chlorine used in water treatment
Chloric (I) acid dissociates in water
HClO(aq) –> H+(aq) + ClO-(aq)
Halides as reducing agents
Halogens decrease in oxidising ability down
Halides (Halogen ions) Increase in reducing ability down
Halide ions act as reducing agents and lose electrons to form halogen molecules
2Cl- –> Cl2 + 2e-
Reactions of Chlorine halide with conc sulphuric acid?
NaCl + H2SO4 –> NaHSO4 + HCl
- Mist fumes
Reaction of Bromine halide with conc sulphuric acid?
NaBr + H2SO4 --> NaHSO4 + HBr Misty fumes Br- ions can reduce sulphur in sulphuric acid to produce SO2 and Br2 Br2 - Brown fumes SO2 - Colourless gas with choking smell
Reaction of Iodine halide with conc sulphuric acid?
NaI + H2SO4 –> NaHSO4 + HI
Misty fumes
I- ions can reduce sulphuric acid to form sulfur dioxide, sulphur and hydrogen sulphide
I2 - Black solid and purple fumes
SO2 - Colourless gas and choking smell
S - Yellow solid
H2S - Colourless gas and rotten egg smell
Testing for halide ions
Silver halides (except silver fluoride) are insoluble and form precipitates.
Sample acidified with dilute nitric acid - prevents other anions such as CO3(2-) forming precipitates
Silver nitrate added
AgCl - White
AgBr - Cream
AgI Yellow
Confirmatory tests
Ammonia added to confirm presence of halide ions
Change in precipitate is measured
Dilute ammonia Conc ammonia
Cl- Dissolves Dissolves
Br- No change Dissolves
I- No change No change
Reactions of halides with water
Hydrogen halides are colourless gases, polar molecules, dissolve in water to form acidic solutions
HF(g) + H20(l) (reversible reaction) H3O+(aq) + F-(aq)
Weak acid ^
HCl(g) + H20(l) –> H3O+(aq) + Cl-(aq)
Strong acid ^
HBr(g) + H20(l) –> H3O+(aq) + Br-(aq)
Strong acid ^
Solubility of silver halides in ammonia?
Decrease in solubility down the group
Soluble ion forms when silver halide dissolves in ammonia solution
AgCl(s) + 2NH3(aq) –> (Ag(NH3)2)+(aq) + Cl-(aq)
Hydrogen halide reactions with ammonia?
Produces ammonium salts
NH3(g) + HCl(g) –> NH4Cl(s)
They are white, ionic solids
