Chapter 10 (Group 7) Flashcards
How does fluorine appear?
Pale yellow gas which is highly reactive
How does chlorine appear?
Green, reactive gas, poisonous in high concentrations
How does bromine appear?
Red liquid, that gives off dense brown/orange poisonous fumes
How does iodine appear?
Shiny grey solid which sublimes to purple gas
State and explain the trend in boiling point down the group
Increases down the group
The molecules become larger as they have more electron shells so have larger Van Der Waals forces between molecules . As the intermolecular forces become larger, they require more energy to break.
Define electronegativity
The relative tendancy of an atom in a molecule to attract electrons in a covalent bond to itself.
State and explain the trend in electronegativity down the group
Decreases down the group
The atomic radius increases as there are more shells and more shielding. The nucleus is less able to attract a bonding pair of electrons.
How does the oxidising power of a halogen change down the group?
Weaker oxidising power
What halide ions is chlorine able to displace?
Iodide and Bromide
What halide ion is bromine able to displace?
Iodide
How does free bromine appear?
Yellow solution
How does free iodine appear in a solution?
Brown solution
How do you identify halide ions?
Add nitric acid and silver nitrate solution and a precipitate should form
Why do you add an acid before identifying halide ions?
To get rid of other negative ions e.g. carbonates
What colour is the precipitate of silver chloride?
White
What colour is the precipitate of silver bromine?
Cream
What colour is the precipice of silver iodide?
Yellow
What is added to help to distinguish between the silver halide precipitates and what is the observation?
Ammonia
Silver Chloride dissolves in dilute ammonia
Silver Bromide dissolves in concentrated ammonia
Silver Iodide does not dissolve/is insoluble in ammonia
How does the reducing power of a halide change down the group and why?
Stronger reducing agent
As the ions get bigger it is easier for the outer electrons to be given away as the electrostatic attraction from the nucleus becomes weaker.
What is a reducing agent?
A species which donate electrons
What type of reaction happens between F- and Cl- and Sulphuric acid and why?
Acid based (proton donor) as the ions are not strong enough reducing agents to reduce the S in sulphuric acid.
What is the equation for sodium fluoride and sulphuric acid and what is the observation?
NaF(s) + H2SO4(l) > NaHSO4(s) + HF(g)
White steamy fumes of HF
What is the equation for sodium chloride and sulphuric acid and what is the observation?
NaCl(s) + H2SO4(l) > NaHSO4(s) + HCl(g)
White steamy fumes of HCl
What is the observation when bromide ions are added to Sulphuric Acid?
White steamy fumes of HBr, Red Fumes of Bromide, Colourless, acidic, chocking gas of SO2.
What is the equation of the acid based step when sodium bromide is added to Sulphuric Acid?
NaBr(s) + H2SO4(l) > NaHSO4(s) + HBr(g)
What is the equation for the Redox step when Hydrogen Bromide reacts with Sulphuric Acid?
2HBr + H2SO4 > Br2(g) + SO2(g) + 2H2O(l)
What is the half equation for the oxidation of Bromide?
2Br- > Br2 +2e-
What is the half equation for the reduction of Sulphuric Acid to form Sulphur Dioxide?
H2SO4 +2H+ + 2e- > SO2 + 2H2O
What is the change of oxidation state of sulphur in H2SO4 > SO2?
6+ > 4+
reduced
What is the change of oxidation state of sulphur in H2SO4 > S?
6+ > 0
reduced
What is the change of oxidation state of sulphur in H2SO4 > H2S?
6+ > 2-
reduced
What is the half equation for the oxidation of iodide?
2I- > I2 + 2e-
What is the equation for the acid-based reaction of Sodium Iodide with Sulphuric Acid?
NaI(s) + H2SO4(l) > NaHSO4(s) + HI(g)
What is the half equation for the reduction of Sulphuric Acid to Sulphur?
H2SO4 + 6H+ + 6e- > SO2 + 4H2O
What is the half equation for the reduction of Sulphuric Acid to Hydrogen Sulphide?
H2SO4 + 8H+ + 8e- > H2S + 4H2O
What is the equation when Hydrogen Iodide reacts with Sulphuric Acid to form Sulphur Dioxide?
2HI + H2SO4 > I2(s) + SO2(g) + 2H2O(l)
What is the equation when Hydrogen Iodide reacts with Sulphuric Acid to form Sulphur?
6HI + H2SO4 > 3I2(s) + S(s) + 4H20(l)
What is the equation when Hydrogen Iodide reacts with Sulphuric Acid to form Hydrogen Sulphide?
8HI + H2SO4 > 4I2(s) + H2S(g) + 4H20(l)
What is the reduction product when Bromide is added to H2SO4?
Sulphur Dioxide
What are the reduction products when Iodide is added to H2SO4?
Sulphur Dioxide, Sulphur and Hydrogen Sulphide
What are the observations when Sodium Iodide is added to H2SO4?
White steamy fumes of HI, Black solid and purple fumes of iodine, colourless and acidic chocking gas of SO2, yellow solid of sulphur and H2S gas with bad egg smell
What is a disproportionation reaction?
A reaction where an element is simultaneously oxides and reduced.
What is the equation for when chlorine is added to water?
Cl2(g) + H2O(l) <> HClO(aq) + HCl(aq)
What is the equation for when chlorine is added to water with sunlight?
2Cl2 + 2H2O > 4HCl (4H+ + 4Cl-) + O2
How is HClO tested for?
Universal indicator/Blue litmus paper will first turn red due to the acidity and then turn colourless as HClO bleaches the colour.
What are the uses for NaClO?
Bleach/Disinfectant
Why can chlorine be added to pools even though it is toxic?
Only added in small quantities to kill bacteria to health benefits outweigh the toxic effects.
What is the equation for the reaction with Chlorine and cold, dilute NaOH?
Cl2(aq) + NaOH(aq) > NaCl(aq) + NaClO(aq) + H2O(l)
