Group 7 Flashcards
(21 cards)
Outline group 7 elements
Highly reactive non-metals - gain an electron to form full shell & 1- ions
Outline the trends in atomic radius trend in group 7
Increases down group - more e- shells
Outline the reactivity trend in group 7
Reactivity decreases down group as more shells - less + nucleus attraction
Outline the ionisation energy trend of group 7
1st ionisation energy decreases as larger radius = more shielding
Outline the boiling point trend of group 7
Simple covalent molecules with vdws forces. Stronger forces down the group due to higher Ar so higher boiling point
Outline the oxidising power trend in group 7
Good oxidising agents - accept e-
Decreases down group as greater radius
Halide displaces one beneath with less oxidising power
e.g Cl2 displaces Br- ions
Outline the halide ion trends in group 7
Good reducing agents - donate e- to species that’s reduced
Reducing power decreases down the group as larger radius/more shielding = e- easier to lose
Outline the reaction & observations of halide ions with H2SO4 (fluoride & chloride)
- NaF + H2SO4 -> NaHSO4 + HF (steamy, white fumes)
- NaCl + H2SO4 -> NaHSO4 + HCl (steamy, white fumes)
Outline the reaction & observation of halide ions with H2SO4 (bromide ions)
NaBr + H2SO4 -> NaHSO4 + Hbr
2HBr + H2SO4 -> Br2 + SO2 + 2H2O
Observation = Orange/brown fumes produced
Outline the reaction & observations of halide ions with H2SO4 (Iodide ions)
NaI + H2SO4 -> NaHSO4 + HI
2HI + H2SO4 -> I2 +SO2 + 2H2O
6HI + SO2 -> H2S + 3I2 + 2H2O
Observations = black solid (S) & purple vapour (I2)
Why are there more reactions when halide ions down the group react with H2SO4?
Higher reducing power so halide can reduce multiple species
Outline the silver nitrate & ammonia test results for identifying halide ions (Cl-, Br-, I-)
+ AgNO3:
F- = No visible change (colourless)
Cl- = White ppt - AgCl
Br- = Cream ppt - AgBr
I- = Yellow ppt - AgI
+ Dilute NH3:
Cl- = ppt dissolves
Br- = No change
I- = No change
+ Conc NH3:
Cl- = ppt dissolves
Br- = ppt dissolves
I- = No change
Why is dilute nitric acid added to silver nitrate for the halide ion test?
Removes OH-/CO3^2- ions that may react with AgNO3 forming a ppt
Outline the reaction of chlorine and water that produces 2 acids.
What type of reaction is it?
Cl2 + H2O -> HCl + HClO
Redox reaction - Cl oxidation state goes from 0 to +1 & -1
Outline the reaction of Chlorine & H2O in the presence of UV light.
What is this used for?
2Cl2 + 2H2O -UV-> 4HCl + O2
Water treatment processes - kills bacteria
Outline reaction of chlorine and sodium hydroxide (cold,aq) and what it’s used for
2NaOH + Cl2 -> NaClO + NaCl + H2O
Produces sodium hypochlorite = ingredient for bleach production
Outline the anion test for sulfate (SO4^2-)
Use BaCl2/Ba(NO3)2 - forms white ppt
Outline the anion test for hydroxide (OH-)
Ions indicate the substance is alkaline - use red litmus paper which turns blue or universal indicator which turns blue-purple
Outline the anion test for carbonates (CO3^2-)
Acid (e.g HCl) is added to a carbonate -> effervescence and CO2 gas
Gas bubbled through limewater which goes cloudy
Outline the cations test for group 2 ions
Use flame tests:
Ca2+ = Brick red flame
Sr2+ = Red flame
Ba2+ = Pale green
Outline the cations test for ammonium (NH4+)
Ammonia gas is given off if NH4+ ions -> hold red litmus paper over petri dish of tested. Turns blue is NH4+ ions present
