4B: elements of group 7 Flashcards
(32 cards)
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
