group 7 Flashcards
what are the appearance and states of G7 elements at RTP
F2–> pale yellow gas
CL2–> pale green gas
BR2–> red brown liquid
I2–> shiny grey-black solid
what is the trend in melting points down group 7
-increases
- more electrons
- stronger london forces
- more energy required to break intermolecular forces
what is the most common type of reactions for halogens
redox
what is the trend in reactivity down group 7
decreases
- atomic radius increases
- more inner shells–> shielding increases
- less nuclear attraction to capture an electron from another species
what are displacement reactions between G7 elements
more reactive halogen displaces halide ion
write the ionic equation for displacement reaction between br- and cl2
CL2 + 2BR- –> 2CL- + BR2
What is a disproportionation reaction
redox reaction where the same element is reduced and oxidised
what are examples of disproportionation reaction
chlorine + water
chlorine + cold dilute NaOH
write the equation and oxidation numbers of the reaction between chlorine and water
Cl2+ H2O–> HClO + HCl
Cl2–> oxidation number goes from 0–> -1
and 0–> +1
what is the equation between chlorine and NaOH
NaOHCl2 + 2NaOH –> NaClO + NaCl +H2O
what are the benefits of chlorine use
-kills harmful bacteria when disinfecting bacteria
- quality of water would be compromised with infectious organisms causing cholera and typhoid without the use of chlorine
what are the risks of using chlorine
- extremely toxic gas
- respiratory irritant in small concentrations–> fatal in large concentrations
- chlorinated water reacts with hydrocarbons (from decaying vegetation) forming chlorinated hydrocarbons–> carcinogens
what is the test for halide ions
presence of Ag+ creates a white precipitate of AgX
