3.2 Inorganic Chemistry: .3 Group 7, the halogens Flashcards
what is the trend in atomic radius down the group 7 elements?
the atoms gets bigger going down the group because each element has one extra filled main level of electrons compared with the one above it
what is electronegativity?
the tendency of a atom to attract the pair of electrons in a covalent bond
what is the trend in electronegativity going down the group 2 elements?
-there is a decrease in electronegativity -as the atoms get larger they become less electronegative -this is because the electrons are further away from the nucleus and are more shielded.
what is the trend in melting/boiling point down the group 2 elements?
-the melting point increases as you down the group -this is because larger atoms have more electrons (higher electron density) -this means that the Van der Waals forces are greater and stronger
the lower the boiling point the more ________ the element.
the lower the boiling point the more volatile the element
what is the trend in oxidising ability down the group 2 elements?
-the elements become less oxidising down the group -this is because as you go down the group the elements become less reactive -this is because the atoms get larger as you go down the group meaning that the outer shell is further away from the nucleus -so electrons are less strongly attracted to it
when will a halogen displace a halide iron?
if the halide is below it in the periodic table -so if the halogen is more reactive than the halide
when an atom gains an element to become a negative ion what do you call it?
-the element is an oxidising agent -this is because it oxidises the other elements (causes other elements to lose an electron) -and it self is reduced because it has gained an electron (RIG- reduction is the gain of electrons)
what is the original colour of chlorine?
very pale green
what is the original colour of Bromine?
orange/brown solution
what is the original colour of Iodine?
brown
give the ionic equation for when Bromine reacts with Potassium iodide and state what you would see.
2KI + Br2 —> 2KBr + I2 -a brown solution is formed (I2)
what halide ion does Fluorine displace?
-Chloride -Bromide - -Iodide
what halide ion does Chlorine displace?
-bromide -iodide
what halide ion does Bromine displace?
-Iodide
what halide ion does Iodine displace?
-non
give the ionic equation for when Chlorine reacts with Potassium bromide and state what you would see.
-2KBr + Cl2 —> 2KCl + Br2 an orange solution is formed (Br2)
give the ionic equation for when Chlorine reacts with Potassium iodide and state what you would see.
-2KI + Cl2 —> 2KCl + I2 -a brown solution is formed(I2)
When potassium iodide and Potassium bromide are formed they both produce brown solutions. how can you tell the distinguish between the two solutions?
- you add an organic solvent (Hydrogen peroxide H2O2)
- Bromine produces a brown solution
- iodine produces a violet solution
what is the trend in the reducing power of halide ions? state why
- the reducing power of halide ionsm increases down the group
- this is because the reducing power of the halogen depends on how well it can lose an electron on its outer shell
- as you go down the group the atoms increase in size which means that the outer electron that needs to be lost is further away from the nucleus
- the outer electron is shielded from the attraction of the nucleus
- This means that the electron is easier to remove
what is the relationhsip between reducing power and reactivity?
the greater the reducing power, the greater the reactivity and the faster the reduction takes place
out of the halogens, which ones reduces Sulphuric acid?
Bromine and Iodine
when reacting halides with concentrated sulphuric acid what state is the halide compound always in?
SOLID
(*so if you see a question like: what is the test for solid NaF then its using hydrochloric acid!!)
How would you test for solid NaF? (create a eqaution)
state what the observations in the reaction would be
state whether it is a redox reaction
state what the H2SO4 acts as in this reaction
- you would add sulfuric acid e.g
- NaF(s) + H2SO4(aq) –> HF(g) + NaHSO4(s)
- you would see misty white fumes produced by the Hydrogen Fluoride
- It is not a redox reaction
- The H2SO4 acts as an acid in this reaction.
How would you test for solid NaCl? (create a eqaution)
state what the observations in the reaction would be
state whether it is a redox reaction
state what the H2SO4 acts as in this reaction
- you would add sulfuric acid e.g
- NaCl(s) + H2SO4(aq) –> HCl(g) + NaHSO4(s)
- you would see misty white fumes produced by the Hydrogen Chloride
- It is not a redox reaction
- The H2SO4 acts as an acid in this reaction.
How would you test for solid NaBr? (create a eqaution)
and what other reactions could take place?
state what the observations in each reaction would be
state whether they are redox reaction
state what the H2SO4 acts as in the reactions
- you would add sulfuric acid e.g
- NaBr(s) + H2SO4(aq) –> HBr(g) + NaHSO4(s)
- you would see misty white fumes produced by the Hydrogen Bromide
- It is not a redox reaction
- The H2SO4 acts as an acid in this reaction.
- There could be another reaction:
2HBr(g) + H2SO4(aq) –> SO2 + Br2 + 2H2O
(in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water)
-for this second reaction you would observe, choking gas (SO2)and orange/brown vapour (Br2)
the second reaction is a redox
Hydrogen Bromide reacts with sulphuric acid
-give the full balanced eqaution for the reaction and state what you would observe
2HBr(g) + H2SO4(aq) –> SO2(g) + Br2(g) + 2H2O(l)
(in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water)
-in this reaction you would observe, choking gas (SO2)and orange/brown vapour (Br2)
this is a redx reaction
How would you test for solid NaI? (create a eqaution)
and what other reactions could take place?
state what the observations in each reaction would be
state whether they are redox reaction
state what the H2SO4 acts as in the reactions
- you would add sulfuric acid e.g
- NaI(s) + H2SO4(aq) –> HI(g) + NaHSO4(s)
- you would see misty white fumes produced by the Hydrogen Iodide
- It is not a redox reaction
- The H2SO4 acts as an acid in this reaction.
- There could be another reaction:
2HI(g) + H2SO4(aq) –> SO2 + I2 + 2H2O
(in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water)
-for this second reaction you would observe, choking gas (SO2)and purple gas/black solid (I2)
the second reaction is a redox
-there could be another reaction:
6HI + H2SO4 –> S+ 3I2 + 4H2O
you would observe a yellow solid (S), a purple gas/black solid (I2)
this is a redox reactoon
-there could be another reaction:
8HI + H2SO4 –> H2S+ 4I2 + 4H2O
you would observe bad egg smell (H2S) and a purple gas/black solid (I2)
Hydrogen iodide reacts with sulphuric acid to form SO2
-give the full balanced eqaution for the reaction and state what you would observe
2HI(g) + H2SO4(aq) –> SO2 + I2 + 2H2O
(in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water)
-for this second reaction you would observe, choking gas (SO2)and purple gas/black solid (I2)
this reaction is a redox
Hydrogen iodide reacts with sulphuric acid to form Sulphur
-give the full balanced eqaution for the reaction and state what you would observe
6HI + H2SO4 –> S + 3I2 + 4H2O
you would observe a yellow solid (S) and a purple gas/black solid (I2)
this is a redox reactoon
Hydrogen iodide reacts with sulphuric acid to form H2S
-give the full balanced eqaution for the reaction and state what you would observe
8HI + H2SO4 –> H2S+ 4I2 + 4H2O
you would observe bad egg smell (H2S) and a purple gas/black solid (I2)
when testing for halides with silver nitrate what state is the halide compound always in?
solution as a precipitate is formed
and for a precipitate to be formed you need two solutions
(*remember* the state symbol for the ion or compound is going to be aqueous)
how would you test for aqueous Fluoride?
give the ionic eqaution for the reaction
and state what you’d observe.
- You would first add dilute nitric acid to remove any ions which might interfere with the test
- Then you add silver nitrate to the solution
- you would just see a colourless solution, no precipitate is formed as no reaction takes place (FIND OUT)
Ag+(aq) + F-(aq) –> AgF(aq)
how would you test for aqueous Chloride?
give the ionic eqaution for the reaction
and state what you’d observe.
- You would first add dilute nitric acid to remove any ions which might interfere with the test
- Then you add silver nitrate to the solution
- you would see a white precipiate
Ag+(aq) + Cl-(aq) –> AgCl(s)
how would you test for aqueous Bromide?
give the ionic eqaution for the reaction
and state what you’d observe.
- You would first add dilute nitric acid to remove any ions which might interfere with the test
- Then you add silver nitrate to the solution
- you would see a cream precipiate
Ag+(aq) + Br-(aq) –> AgBr(s)
how would you test for aqueous Iodide?
give the ionic eqaution for the reaction
and state what you’d observe.
- You would first add dilute nitric acid to remove any ions which might interfere with the test
- Then you add silver nitrate to the solution
- you would see a yellow precipiate
Ag+(aq) + I-(aq) –> AgI(s)
out of the halide ions which forms a precipitate with silver ions the fastest?
Iodide
out of the halide ions which forms the precipitate with silve ions tthe slowest?
chloride
to be extra sure you can test your results (from testing halide ions with silver nitrate) with ammonia solution.
(*remember*: this is only used on the precipitates so fluorine cant be tested with ammonia since it did not form a precipitate)
You might do this because the colour variations are pretty similar betweent the halide ions so this distinguishes them more
what is the effect of Concentrated and dilute ammonia solutions on silver chloride precipitate?
they both dissolve the Silver Chloride
-so it is soluble in both solutions
what is the effect of Concentrated and dilute ammonia solutions on silver bromide precipitate?
the dilute ammonia solution does not dissolve the silver bromide but the concentrated does
-so silver bromide is insoluble in dilute ammonia solution but in soluble in concentrated ammonia solution
what is the effect of Concentrated and dilute ammonia solutions on silver iodide precipitate?
silver iodide does not dissolve in niether of the solutions
-so silver iodide is insoluble in both concentrated and dilute ammonia solutions
(*remember*: I I I, iodine is insoluble)
give the eqaution where common household bleach is produced
in this reaction chlorine is both oxidised and reduced, what is this called?
2NaOH(aq) + Cl2(g) –> NaClO(aq) + NaCl(aq) + H2O(l)
the NaClO is your bleach
disproportionation
what is called when a elements is both reduced and oxidised in a reaction?
disproportionation
give the ionic eqaution for when chlorine is mixed with water producing chlorate and chloride ions
why is this reaction used for the safety of swimming pools?
Cl2(g) + H2O(l) <–> 2H+(aq) + Cl-(aq) + ClO- (aq)
chlorate ions (ClO-) kill bacteria
give the symbol eqaution for when chlorine reacts with water in sunlight
Cl2(g) + 2H2O <—> 4H+(aq) + 2Cl- + O2
what are uses of chlorine in water treatment?
- kills disease causing microorganisms
- some chlorine persists in the warer and prevents reinfection further down the supple
- it prevents the growth of algae, eliminating bad tatses and smells, and discoulouration caused by organic compounds
what are the risks that arise from using chlorine to treat water
- chlorine gas is very harmful it it’s breather in- it irritates the respiratory system
- liquid chlorine can cause severe chemical burns on skin and eyes
- water contains a variety of organic compounds, chlorine reacts with these compounds to form chlorinated hydrocarbons e.g chloromethane
many of these chlorinated hydrocarbons are carcinogenic (however increased cancer risk is small compared to the risk from untreated water)
