10 - Group 7 Halogens Flashcards
Describe and explain the trend of Group 7 electronegativity.
- Decreases down Group 7
- Down group, number of electro shells increases
- Atomic radii increases
- Ability of nucleus to attract bonding pair decreases
Describe and explain the trend in boiling points of Group 2.
- Increases down group
- Number of electrons increases
- Number of van der Waals increases
- Energy required to seperate molecules increases
Describe the trend in oxidising ability of Group 7.
Decreases down group
Define, in terms of electrons, an oxidising agent.
Electron acceptor
What colour is a bromine solution?
Brown maybe
Give the colours of an iodine solution, iodine solid, and iodine gas.
Brown solution
Black solid
Purple gas
What colour is a chlorine solution?
Very pale green, or colourless
Describe the test for a halide ion?
- Add nitric acid
- Add silver nitrate
- Add ammonia
Why is nitric acid added to a halide test?
Reacts with carbonates which would otherwise form Ag2CO3
Describe the precipitates formed in a silver halide test.
- Fluoride forms no preciptate
- Chloride forms a white precipitate
- Bromine forms a cream precipitate
- Iodide forms a yellow precipitate
| - Silver chloride dissolves in dilute ammonia
- Silver bromide dissolves in concentrated ammonia
- Silver iodide does not dissolve in ammonia
Describe and explain the trend in reducing ability in Group 7.
- Increases down group
- More electron shells
- Larger atomic radius
- Less electrostatic attraction
- Easier to remove an electron
What is a reducing agent, in terms of electrons?
Electron donor/loses electrons
What kind of reactions occur when fluoride and chloride ions react with concentrated sulfuric acid?
Acid-base
Write down the equation for a recation between NaF (or Cl) and concentrated sulfuric acid.
Include state symbols.
NaF (s) + H2SO4 (l) –> NaHSO4 (s) + HF (g)
Describe what you would see when NaF (or Cl) reacts with concentrated sulfuric acid.
Steamy white fumes (of HF or HCl)
Write down the equations for a reaction between NaBr and concentrated sulfuric acid.
Include state symbols.
- NaBr (s) + H2SO4 (l) –> NaHSO4 (s) + HBr (g)
- 2H+ + 2Br- + H2SO4 (l) –> Br2 (g) + So2 (g) + 2H2O (l)
Describe (physically) the products of the reaction between NaBr and concentrated H2SO4.
White steamy fumes (of HBr)
Orange fumes (of Br2)
Colourless, acidic gas (SO2)
Write down the equations for the reaction between NaI and concentrated H2SO4.
Include state symbols.
- NaI (s) + H2SO4 (l) –> NaHSO4 (s) + HI (g)
- 2H+ + 2I- + H2SO4 (l) –> I2 (s) + SO2 (g) + 2H2O (l)
- 6H+ + 6I- + H2SO4 –> 3I2 (s) + S (s) + 4H2O (l)
- 8H+ + 8I- + H2SO4 –> 4I2 (s) + H2S (g) + 4H2O (l)
Describe (physically) the products of the reaction between NaI and concentrated sulfuric acid. (6)
White steamy fumes (HI)
Black solid (I2)
Purple fumes (I2)
Colourless, acidic gas (SO2)
Yellow solid (S)
Gas with bad egg smell (H2S)
What is a disproportionation reaction?
Where an element is both oxidised and reduced.
Write an equation for the reaction of gaseous chlorine with water, without the presence of sunlight.
Include state symbols
Cl2 (g) + H2O (l) <–> HClO (aq) + HCl (aq)
Write an equation for the reaction of gaseous chlorine with water, with the -presence of sunlight.
Include state symbols.
2Cl2 (g) + 2H2O (l) –> 4H+ + 4Cl- + O2
Write an equation for the reaction of Cl2 with cold, dilute, aquaeous NaOH, and describe the use of the products of this reaction.
Include state symbols.
Cl2 (aq) + NaOH (aq) –> NaCl (aq) + NaClO (aq) + H2O (l)
NaCl and NaClO are used in conjuction as a bleach and disinfectant to kill bacteria.
What occurs when Cl2 reacts with KBr?
Equation (state symbols) + observations
Cl2 (aq) + 2K+ (aq) + 2Br- (aq) –> 2K+ (aq) +2Cl- (aq) + Br2 (aq)
Yellow solution (due to Br2)
Describe fluorine at room temperature.
Very pale yellow gas
Highly reactive
Describe chlorine at room temperature.
Greenish gas, poisonous in high concentrations
Reactive
Describe bromine at room temperature.
Red liquid, that gives poisonous orange/brown fumes
Describe iodine at room temperature.
Shiny grey solid which sublimes to purple gas
