Flashcards
Chapter 8- group 7
Flashcards do conjunto (27)
- 1what is the name for Group 7 elementshalogens
- 2describe halogens briefly-highly reactive non metals
-diatomic molecules (2 atoms 1 cov bond) - 3outer electronic config of halogenss2p5
- 4what happens to bpt/mpt down the group and why-increases
-as london forces (induced dipole-dipole interactions) get stronger cuz size & relative mass of atoms increases - 5what affect does this trend in mpt/bpt hav-from chlorine gas to iodine solid
- 6why are the halogens said to be oxidising agents?-react by gaining 1 electron forming 1- ions
-so theyre reduced and they oxidise something else (redox reaction) - 7what happens to halogen reactivity down the group?decreases
- 8why do the halogens get less reactive down the group (less oxidising)?-atomic radii increases
-so outer es further from nucleus
-outer es shielded more from attraction of +nucleus as there are more inner electrons
-so harder for larger atos to attract electron needed to form ion despite increases charge on nucleus, so larger atoms less reactive - 9what colour is fluorine and what state?pale yellow gas
- 10what colour is chlorine and what state?green gas
- 11what colour is bromine and what state?red-brown liquid
- 12what colour is iodine and what stategrey solid
- 13what backs up the decreasing trend in reactivity down the group?their displacement reactions with halide ions
-halogens displace less reactive halide ions from solution - 14explain what happens in these displacement reactions with example-if you mix bromine (higher than iodine in reactivity series than iodine so more reactive) with potassium iodide solution (halide) the bromine displaces the iodide ions (oxidising them), giving iodine and potassium bromides solution
- 15bromine displacing iodine equation
- 16explain what the coloured precipitate indicates in these redox reactions- the less reactive halogen will be displaced so if you add a hexane solvent to mixture the less reactive one will appear as a layer on top
-colour of layer tells u what was displaced
-if browny orange bromine was displaced, if purple iodine was displaced - 17table of halogen halide displacement reaction results
- 18test for halide ions-first add dilute nitric acid HNO3
(removes impurities ions)
-then add SILVER NITRATE SOL
AgNO3
coloured ppt= silver halide forms
Ag(aq)+ X- --> AgX
then add NH3 sol for solubility--> larger ion more insoluble - 19halide ion identification: AgCl ion colour & is it soluble in NH3?CL-
white ppt
dissolves in dilute NH3 - 20halide ion identification AgBr colour of ppt & soluble in NH3?Br-
cream ppt
dissolves yes, but in CONC NH3 - 21halide ion identification AgI ppt colour & is it soluble in NH3?I-
yellow ppt
NO! insoluble in NH3 - 22disproportionation (halogens can undergo this)reaction in which an element is simultaneously oxidised & reduced
- 23halogen disproportionation example: forming bleachChlorine + cold dilute aq NaOH
sodium chlorate forms (households bleach)
2NaOH + CL2--> NaClO + NaCl + H2O
ox number of Cl goes up to +1
& down to -1 - 24halogen disproportionation example: water treatmentCl2 + H2O ⇌ HCLO + HCL
chlorine + water--> chloric acid + HCL
then...
HCLO + H2O ⇌ CLO- + H3O+
HCLO add water forms chlorate ions
chlorate then kill bacteria in water - 25pros of using chlorine for water treatmentkills disease causing microorganisms
some CL remanes in H20 so prevents reinfection
prevents algae growth, no bad smells, gets rid of discolouration - 26risks of using chlorine-Cl2 very harmful if inhaled
(irritates resp system)
-liquid Cl burns skin/eyes
-Water ha slots of compounds e.g e.g from plant decomp, CL reacts with them to form Chlorinated hydrocarbons, e.g CH3CL--> carcinogenic
-ethical considerations--> not our choice - 27alt to chlorine in water treatmentO3 ozone
- strong ox agent, kills MOs but expensive & short half life so not LR
UV
-kills MOs by DNA damage, but ineffective in cloudy water & no LR
Informações
- Descrição
- A level Chemistry (Module 3 Periodicity table and energy) FlashCards sobre Chapter 8- group 7 , criado por Mehak Zahrah Faheem em 05-01-2019.
- Criado por
- Mehak Zahrah Faheem
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