Group 7 Flashcards
what is a halide
negative ions (anions) of group 7 e.g. Cl-
what is a halogen
uncharged diatomic molecules of group 7 e.g. Cl2
reducing ability of the halides
larger the ionic radius the better the reducing agent because the attraction from the nucleus to the outer electrons are weaker so the outer electron is easier to lose
observation of reaction of NaX and conc H2SO4
halide : products : observation
Cl- : HCl : white steamy fumes, fizzing
Br- : HBr : steamy fumes
Br- : Br2 : brown fumes
Br- : SO2 : colourless gas, choking odour
I- : HI : steamy fumes
I- : I2 : black solid
I- : SO2 : colourless gas choking odour
I- : S : yellow solid
I- : H2S : gas (bad egg smell)
what is the trend in electronegativity down group 7
decreases down the group, the atomic radius of the elements increase which means that the outer shells get further away from the nucleus
what is the trend in boiling point down the group
increases down the group as van der waals forces get stronger between molecules as the molecule gets bigger
trend in oxidising ability down the group
decreases down the group as ability to attract electrons is decreased due to shielding as there is greater atomic radius
trend in reducing ability
can displace any ion below it
how to test for halides
add hno3 which removes any interfering ions
add silver nitrate to produce a coloured precipitate of agx
the identity of the agx ca be found by testing its solubility in nh3
results from testing for halides
halide - observation agno3 - dilute nh3 - conc no3
F- : colourless ppt : - : -
Cl- : white ppt : dissolves : -
Br- : cream ppt : insoluble : dissolves
I- : yellow ppt : insoluble : insoluble
reaction of chlorine and water
benefits and drawbacks of using chlorine in water
benefits
- kills microorganisms to make water safe to drink
- easy to handle and fast acting
- keeps water safe to drink
drawbacks
- at high concentration cl can be harmful
BENEFITS OUTWEIGH THE RISK SO WE USE CL TO REMOVE HARMFUL MICROORGANISMS
ADD IN EQUATIONS FROM 3.2.3.2
