Halogens Flashcards
Give the colour of fluorine, chlorine, bromine and iodine at room temperature and pressure.
Fluorine - Yellow gas
Chlorine - Yellow-Green gas
Bromine - Red-Brown liquid (vapour when heated)
Iodine - Grey-Black solid (purple vapour when heated)
What is the trend in m.p/b.p down the halogens and why?
Increased due to increased Van der Waals
What is the trend in electronegativity, first ionisation energy and atomic radius.
Decreases - 1st I.E and electronegativity
Increases - Atomic radius
Outer electrons are further form the nucleus.
What are the halogens?
Non-polar simple covalent molecules
What happens to the solubility of the halogens down the group?
Decreases down the group until iodine which is virtually insoluble in water.
What do all of the halogens dissolve in?
Non-polar solvents such as hexane because like dissolves like (The halogens are non-polar)
Give the colour of the solution Chlorine, Bromine and Iodine make with water.
Chlorine - Green solution
Bromine - Yellow solution
Iodine - virtually insoluble but any solution is Brown
Give the colour of the solution Chlorine, Bromine and Iodine make with hexane.
Chlorine - Colourless solution
Bromine - Red solution
Iodine - Purple solution
Give the reaction of the halogens with water and what are they an example of?
Cl2 + H2O → HOCl + HCl
This is an example of a disproportionation reaction.
Write the equation and ionic equation for chlorine and cold dilute sodium hydroxide solution
2NaOH + Cl2→ NaCl + NaClO + H2O
2OH- + Cl2 → Cl- + ClO- + H2O
What is the name of NaClO
Sodium Hypochlorite or Sodium Chlorate (1) because it contains the Chlorate(1) ion ClO-
Write the equation and ionic equation for Chlorine and hot concentrated sodium hydroxide solution.
3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O
6OH- + 3Cl2 → 5Cl- + ClO3- + 3H2O
What is the name of NaClO3
Sodium Chlorate (V) because it contains the chlorate (V) ion.
In what ways do Iodine and bromine react with both hot concentrated and cold dilute NaOH?
Bromine reacts in the same was as chlorine but Iodine does not react with cold dilute NaOH only hot concentrated NaOH.
What is the observations for the above reactions with chlorine?
The yellow-green gas dissolves to form a colourless solution.
Describe the oxidising ability of the halogens.
Oxidising ability decreases as atomic number increases.
Oxidising agents cause another species to lose electrons it itself gaining electrons and becoming reduced.
Oxidising agents readily accept electrons
The ease at which an oxidising agent gains electrons is a measure of how effective an oxidising agent it is.
The halogens gain electrons in their outer layer in order to complete their energy level.
The outer electrons are closer to the nucleus in fluorine
The electron fluorine gains is more attracted to the nucleus because it is closer then chlorine.
There is more shielding down the group therefore attraction to the nucleus is not as strong
Which of the halogens will displace which?
Fluorine will displace all other halides in solution.
Chlorine can displace Br and I in solution
Br can displace I
I can displace none except Astatine
Whats the colour change when Chlorine reacts with Iodide ions?
Colourless to Yellow
What is the colour change when Bromine reacts with Iodide ions?
Solution darkens from orange to brown
Describe the reducing ability of the Halogens
Reducing ability increases as Atomic number increases
Reducing agents cause another species to gain electrons, itself becoming oxidised
Reducing agents readily donate electrons
The ease with which a reducing agent loses its electrons determines how effective it is as a reducing agent
The electron lost by an iodide ion comes from an energy level with more shielding and further from the nucleus, therefore, it is more easily lost
Fluorine and Chlorine have little reducing ability
What is the equation of fluoride reacting with concentrated sulfuric acid?
NaF + H2SO4 → NaHSO4 + HF
Does HF have any reducing ability?
No
What are the observations?
Misty fumes, heat releases, gas produced, solid disappears, pungent smell
What are the names of the products
Sodium hydrogensulfate and Hydrogen fluoride
Write the equation for the reaction of chloride with concentrated sulfuric acid
NaCl + H2SO4 → NaHSO4 + HCl
Does HCl have any reducing ability?
No
What are the observations?
Misty fumes, heat released, gas produced, solid disappears, pungent smell
What are the names of the products?
Sodium hydrogensulfate and hydrogen chloride
Write the equation for Bromide with concentrated sulfuric acid
NaBr + H2SO4 → NaHSO4 + HBr
2HBr + H2SO4 → Br2 + SO2 + 2H2O
Does HBr have any reducing ability?
Some, H2SO4 is reduced to SO2 and Bromide is oxidised to Br2
What are the observations?
Misty fumes, heat released, gas produced, solid disappears, red-brown vapour, pungent smell
Write the equations for the reaction of Iodide with concentrated sulfuric acid.
NaI + H2SO4 → NaHSO4 + HI
2HI + H2SO4 → I2 + SO2 + 2H20
6HI + H2SO4 → S + 3I2 + 4H20
8HI + H2SO4 → H2S + 4I2 + 4H2O
Does HI have any reducing ability?
Yes lots, H2SO4 is reduced to SO2, S and H2S while iodide is oxidised to I2
Observations
Misty fumes, heat released, solid disappears, gas produced, purple vapour, grey-black solid, pungent smell, rotten eggs smell, yellow solid.
How can the reaction of chloride and concentrated H2SO4 show that chloride ions are present?
The reaction gives off HCl, which when tested using a glass rod dipped in concentrated ammonia solution gives off a white smoke.
How can the reaction of bromide ions with concentrated sulfuric acid show that there are bromide ions present
Red-brown vapour/fumes given off
How can the reaction of Iodide ions with concentrated sulfuric acid show that Iodide ions are present?
Purple vapour and a grey-black solid forms
What is the name of the H2PO4^- ion called?
The dihydrogenPHOSPHATE ion
What is the reaction for NaF, NaCl, KBr and KI with concentrated Phosphoric acid?
NaF + H3PO4 → NaH2PO4 + HF
NaCl + H3PO4 → NaH2PO4 + HCl
KBr + H3PO4 → KH2PO4 + HBr
KI + H3PO4 → KH2PO4 + HI
How is ozone generated?
By passing hight voltage electrical discharge through oxygen, or using UV light
What is the equation for the production of ozone?
3O2 → 2O3
How do chlorine and ozone kill microorganisms?
The oxidise them
Compare and contrast ozone to Chlorine as a method of treating drinking water.
Advantages Chlorine:
1) Cheaper than Ozone
2) Remains in the water → residual protection
3) More soluble than ozone
Disadvantages Chlorine:
1) Cannot kill some microorganisms
2) Leaves chemicals in the water
3) Unpleasant taste
4) Toxic to humans
Advantages Ozone:
1) Kills more types of microorganism than chlorine
2) Breakdown product is oxygen
3) No residual chemicals in the water
4) Removals metal and organic particles from the water
Disadvantages Ozone:
1) More expensive than chlorine
2) Does not provide residual protection
3) Less soluble so special mixing techniques needed
