halogens Flashcards
F2 colours + reactivity
very pale yellow gas
highly reactive
Cl2 colours + reactivity
greenish
reactive gas
poisonous in high con
Br2 colours + reactivity
red liquid
dense brown/orange poisonous fumes
I2 colours + reactivity
shiny grey solid
sublimes to purple gas
trend in boiling + melting point
increases down group
molecules get larger = more electrons
=larger van der waals between molecules
larger intermolecular force = more energy needed to break forces
define electronegativity
relative tendency of a molecule to attract a bonding pair of electrons to itself in a covalent bond.
trend in electronegativity
decreases down group
atomic radii increases down group as no. of shells increase
= nucleus less able to attract bonding pair of electrons
what are oxidising agents
electron acceptors
does oxidising strength increase or decrease down group?
decrease
what will a halogen that is a stronger oxidising agent do?
replace a halogen with less oxidising power
what colour does chlorine have if it’s a free halogen in a displacement reaction
very pale green
what colour does bromine have if it’s a free halogen in a displacement reaction
yellow solution
what colour does iodine have if it’s a free halogen in a displacement reaction
brown solution
sometimes black solid
write the half equations for the displacement reaction for Cl2(aq) + 2Br –(aq) → 2Cl –(aq) + Br2(aq)
2Br - (aq)→ Br2(aq)+ 2e-
Cl2(aq)+ 2e- → 2Cl- (aq)
why is a halide ion with silver nitrate test used
to identify the halide ion
what chemicals are used in a silver nitrate test
nitric acid - to make solution acidic
silver nitrate - added dropwise
what is the role of nitric acid in a silver nitrate test
react with carbonates present
to prevent ppt of Ag2Co3- would mask desired products
write the reaction between nitric acid and sodium carbonate
2 HNO3 + Na2CO3 →2 NaNO3 + H2O + CO2
what do fluorides produce with silver nitrate and nitric acid
no ppt
what do chlorides produce with silver nitrate and nitric acid
white ppt
write the ionic equation for the reaction of chlorine with silver nitrate and citric acid
Ag+(aq) + Cl- (aq) → AgCl(s)
what do bromides produce with silver nitrate and nitric acid
cream ppt