Group 7 Flashcards
What is the trend of electronegativity?
Decreases because the number of shells increases so there’s a weaker attraction between nucleus and electrons in a covalent bond.
What is the trend in BP and MP?
Increases, more VDW between molecules that need to be broken.
What does fluorine look like at room temperature?
Pale yellow gas.
What does chlorine look like at room temperature?
Pale green gas.
What does bromine look like at room temperature?
Red-orange liquid.
What does iodine look like at room temperature?
Black solid.
What is an oxidising agent?
An electron acceptor.
What acts as oxidising agents?
Halogen atoms.
What is the strongest oxidising agent?
Fluorine.
What happens to the ability to act as an oxidising agent down the group?
Decreases, atomic radius and shielding increases so become harder to gain electron.
What are the three displacement reactions?
1) Cl2 + 2Br- ~> Br2 + 2Cl- (yellow/orange solution)
2) Cl2 + 2I- ~> I2 + 2Cl- (brown solution)
3) Br2 + 2I- ~> I2 + 2Br- (brown solution).
What is a reducing agent?
Electron donor.
What happens to the ability to act as a reducing agent down the group?
Increases, size increases so electrons further away from nucleus so less attraction.
What reaction do all halides do?
Acid-base reaction.
What is the general equation for an acid-base reaction?
NaX + H2SO4 ~> NaHSO4 + HX
(swap the Na and a H)
What is the observation in an acid-base reaction?
Misty fumes (HX).
What are the possible products of a halide ion redox reaction?
HX, SO2, S, H2S.
What redox reaction can each halide undergo?
F and Cl acid base only.
Br acid base and SO2.
I acid base, SO2, S and H2S.
What are the observations in redox reactions?
SO2- choking gas
S- yellow solid
H2S- rotten egg smell
Br2- brown gas
I2- black solid + purple gas.
How can halide ions be identified?
Add acidified silver nitrate.
What is the ionic equation for halide ions and silver nitrate?
Ag+ + X- ~> AgX.
What precipitates do silver halides create?
AgCl- white ppt
AgBr- cream ppt
AgI- yellow ppt.
What do we acidify silver with? Why?
Nitric acid because hydroxide and carbonate ions also form a precipitate with silver ions so need to be removed.
What do we add to silver halides to confirm their identity?
Ammonia.
How do halides react in different concentrations of ammonia?
Dilute ammonia- AgCl soluble, AgBr sparingly soluble, AgI insoluble.
Conc ammonia- AgBr- soluble AgI- insoluble.
What is the general equation when silver halides react with ammonia?
AgCl + 2NH3 ~> Ag(NH3)2+ + Cl-.
What is the equation for chlorine water?
Cl2 + H2O ~><~ HCl(aq) + HClO(aq).
What is the use of HClO?
Bleach.
What does chlorine do in the presence of bright sunlight?
2Cl2 + H2O ~> 4HCl + O2
pale green gas ~> colourless.
Why can chlorine be used in water treatment even though it’s toxic?
It’s used in low concentrations or small amounts.
What is a use of chlorine in water treatment?
Kill bacteria.
What is the equation for Cl reacting with cold dilute sodium hydroxide?
Cl2 + 2NaOH ~> H2O + NaCl + NaClO.
NaClO is used in household bleach.
What are the steps in filtering?
1) Filter using gravity
2) Wash residue with water to remove soluble impurities
3) Dry in air to remove water.
