4B: elements of group 7 Flashcards
describe the nature & colour of F2.
highly reactive, pale yellow gas
describe the nature & colour of Cl2.
pale green gas, poisonous in high reactions
describe the nature & colour of Br2.
red liquid, dense brown / orange poisonous fumes
describe the nature & colour of I2.
grey solid, sublimes in purple gas
what is the definition of electronegativity?
relevant tendency of an atom in a molecule to attract e- in a covalent bond to itself
what is the trend of electronegativity down group 7? why?
electronegativity decreases down the group
- increasing atomic radii as higher number of shells
- nucleus less able to attract bonding pair of e-
what is the trend of melting / boiling point down group 7? why?
increases down the group
- more e- & stronger london forces & therefore more energy needed to overcome
explain the reactivity of group 7 down the group.
reactivity decreases down the group
- atoms get bigger with more shielding -> less easily attract 1 e-
describe the oxidising strength down group 7.
oxidising strength decreases down group 7 & will displace a halogen with lower oxidising power from 1 of its compounds
what colour will be shown in the solution if KBr is reacted with Cl2? explain why.
yellow
- Cl displaces Br
what colour will be shown in the solution if KI is reacted with Cl2? explain why.
brown
- Cl displaces I
what colour will be shown in the solution if KI is reacted with Br2? explain why.
brown
- Br displaces I
what colour will be shown in the organic layer if KBr is reacted with Cl2? explain why.
yellow
- Cl displaces Br
what colour will be shown in the organic layer if KI is reacted with Cl2? explain why.
purple
- Cl displaces I
what colour will be shown in the organic layer if KI is reacted with Br2? explain why.
purple
- Br displaces I
which halogens will oxidise iron from 2+ to 3+?
Cl & Br
which halogen will reduce iron from 3+ to 2+?
I
state the disproportionation reaction of Cl which forms bleach.
Cl2 (g) + H2O (l) -> HClO (aq) + HCl (aq)
if indicator is used in the disproportionation reaction of Cl, what will the observations be?
solution turns red & turns colourless as HClO bleaches the colour
what conditions will halogens react with cold dilute NaOH? what observations will they be?
in aqueous solutions
- colour fades to colourless
what happens when halogens are reacted with hot dilute NaOH?
disproportionation occurs
what are the products of Cl2 reacting with cold dilute NaOH?
NaCl (aq) + NaClO (aq) + H2O (l)
what are the products of Cl reacting with hot dilute NaOH?
5 NaCl (aq) + NaClO3 (aq) + 3 H2O (l)
what are the reaction type of conc. sulfuric acid with group 1 halides (Cl & F) ? why?
acid-base
- sulfuric acid is not strong enough to oxidise Cl & F
what will be observed when conc. sulfuric acid reacts with group 1 halides (Cl & F)?
white steamy fumes of HF / HCl
describe & explain the trend down group 7 as reducing agents.
increasing strength down the group
- greater tendency to donate e- as outer e- is easier to give away
what is the colour of S?
yellow
how could H2S be distinguished?
bad egg smell
how could halides be tested?
1) add nitric acid to remove any present carbonate
2) add silver nitrate
which halogen does not form a precipitate with silver nitrate test?
F
what will be formed when a hydrogen halide reacts with water?
H3O+ + (halide)-
[acidic solution]
what will be formed & observed when hydrogen halides react with ammonia?
forms ammonium halides (white smoke)
