group 17 Flashcards
give formulas, colours, states of:
- fluorine
- chlorine
- bromine
- iodine
- F2, pale yellow, gas
- Cl2, pale green, gas
- Br2, brown-red, liquid
- I2, grey, solid (purple vapour)
explain trend in boiling point DOWN the group
boiling point increases going DOWN
- more electrons
- stronger london forces
- between molecules
- more energy needed to overcome
explain how london forces form
- electron cloud is constantly moving
- at any one moment, there is an uneven distribution of electrons
- forms temporary dipole
- induces a dipole in neighbouring molecule
- attractive forces between molecules
explain trend in reactivity going DOWN the group
P- more protons
S- more shielding
D- increased distance between nucleus and outer electron
S- strength of attraction decreases
harder to gain an electron
have 7 outer electrons, want to gain 1 more
what is a displacement reaction
more reactive element displaces less reactive element from its compound in solution
give colour of Cl, Br, I when dissolved in water
Cl- pale green
Br- orange
I- brown
give colour of Cl, Br, I when dissolved in organic solvent (easier to see)
Cl- pale green
Br- orange
I- purple
explain why chlorine is a stronger oxidising agent than bromine
- to act as oxidising agent the chlorine must gain 1 electron and be reduced
- Cl atom is smaller and more reactive than Br so gains electron more easily
- electron is more strongly attracted to nucleus and held more strongly by Cl
what is a disproportionation reaction
an element is simultaneously oxidised and reduced
when does a disproportionation occur
halogen + water
halogen + cold alkali
Cl2 + H20 -> ?
HCL + HCLO(chloric(I) acid)
give formula of bleach
NaClO
give equation for chlorine and dilute, aqueous sodium hydroxide
Cl2 + 2NaOH -> NaCl + NaClO + H2O
why can you not use a bleach with acid ( give the equation )
forms toxic Cl gas
NaClO + HCL -> Cl2 + NaCl + H2O
give one benefit of chlorine
used in drinking water as it kills bacteria- prevents cholera
