Group 7 Flashcards
What are group 7 ions called?
Halides
What do the halogens look like at room temperature?
Fluorine - pale yellow gas
Chlorine - green gas
Bromine - red brown liquid
Iodine - black/ dark grey solid
What type of molecules do halogens form?
Diatomic molecules
What happens to electronegativity down group 7?
Decreases (more shielding and e-s further away from nucleus)
What happens to boiling point down group 7?
Increases (van der Waals forces increase due to larger size of molecules)
What do halogens act as in redox reactions?
Oxidising agents (gain electrons)
What happens to the oxidising ability of halogens down group 7?
Decreases, so halogens lower down will be displaced by halogens higher up (forming diatomic molecule of the halogen lower down)
What happens to the reducing ability of halides down group 7?
Increases
What type of reaction do fluoride and chloride ions have with sulfuric acid?
Acid-base (oxidation states stay the same)
e.g. for all group 7= NaF + H2SO4 —> NaHSO4 + HF(g)
Produces steamy fumes
Why type of reactions do sodium bromide and sodium iodide have with sulfuric acid?
Acid-base and redox
What is the equation for the redox reaction between NaBr and sulfuric acid?
2H+ + 2Br-(s) + H2SO4(l) –> SO2(g) + 2H2O(l) + Br2(l)
Produces brown fumes
What is the equation for the redox reaction between NaI and sulfuric acid?
8H+ + 8I- + H2SO4(l) –> H2S(g) + 4H2O(l) + 4I2(s)
Sulfur briefly seen as yellow solid. Produces hydrogen sulfide gas (smells like rotten eggs), iodine as black solid, and some purple fumes (some solid vaporises).
How do you identify halides using silver nitrate?
-Dissolve in water to form aqueous solution
-Add few drops of silver nitrate
-Halides react with silver to form a silver halide (X-(aq) + Ag+(aq) –> AgX(aq) )
What observations are made when AgF forms?
Soluble in water so no observable change (no precipitate)
What observations are made when AgCl forms?
White precipitate
