4. Inorganic Chemistry (GROUP 7 HALOGENS)) Flashcards
Give the ionic equation between silver nitrate and halide ions during the precipitate reaction which tests for halides
Ag+ (aq) + X- (aq) either Cl,Br,I —> AgX (s) either AgCl,AgBr,AgI
Describe how to test for halide ions and the observations you would see
Add dilute nitric acid to solution - prevents formation of silver precipitate
Add silver nitrate
Would form a precipitate:
Chlorine ions - white precipitate
Bromide ions - cream precipitate
Iodide ions - yellow precipitate
–> Afterwards, can add an organic solvent which will dissolve precipitate to better understand which halogen is present
Give the trend for electronegativity down group 7
Electronegativity down group 7 decreases as the atomic radius increases due to higher number of shells and more shielding so the bonding electrons in the covalent bond are further from the nucleus so there is less attraction so the bonding electrons are pulled less to the nucleus
Give the trend for reactivity down group 7
Reactivity down group 7 decreases as the atom gets larger with more shells so the outer shell electron is more shielded from the nucleus resulting in decreased electrostatic forces of attraction do it is harder to attract an electron
Describe the trend for melting and boiling point for group 7
Increase down the group
As the molecules become larger they have more electrons and so have larger London forces so more energy required to break the forces. This increases the melting and boiling points
Give the colour of the following halogens in water (after they have been displaced by a more reactive halogen):
Chlorine
Bromine
Iodine
Chlorine - pale green often colourless solution
Bromine - yellow solution
Iodine - brown solution
Give the colour changes when an organic solvent is added to aqueous halogens
chlorine: pale green to colourless
bromine: yellow solution remains yellow or brown
iodine: brown to purple
Describe the reaction between a halogen (eg:chlorine) and cold and hot sodium hydroxide -NaOH
The colour of solution fades to colourless forming e.g. NaClO and NaCl and H20
Cl2(aq) + 2NaOH(aq) –> NaCl (aq) + NaClO (aq) + H2O(l)
- hot is similar however halogen reaches a higher oxidation state and forms ClO3
Describe the trend of the reducing power of halides
Increases down the group
They have a greater tendency to donate electrons.
This is because as the ions get bigger it is easier for the outer electrons to be given away as the pull from the nucleus is smaller.
What would be produced and what would you see with the reaction of:
Fluorine and sulfuric acid
Chlorine and sulfuric acid
Steamy white fumes
F- and Cl- ions are not strong enough reducing agents to reduce the S in H2SO4
. No redox reactions occur. Only acid-base reactions occur.
What would be produced and what would you see with the reaction of:
Bromine and sulfuric acid
Br- ions are stronger reducing agents than Cl- and F- and reduce the S from +6 to +4
Produces white steamy fumes of HBr
orange fumes of bromine are also
evolved and a colourless, acidic gas
What would be produced and what would you see with the reaction of:
Iodine and sulfuric acid
I- ions are the strongest halide reducing agents. They can reduce the sulfur from +6 in H2SO4
to + 4 in SO2 , to 0 in S and -2 in H2S.
White steamy fumes of HI are evolved.
Black solid and purple fumes of Iodine are
also evolved
A colourless, acidic gas SO2
A yellow solid of sulfur
H2S (Hydrogen sulfide), a gas with a bad egg
smell
