ES 1- The Halogens Flashcards
What kind of ions do all group 7 elements form?
-1 ions (gain 1 electron)
Are halogens oxidising or reducing agents?
Oxidising agents; they are reduced by gaining 1 electron
Halogens are reduced to…
Halides
Halogens occur as diatomic molecules. What does this mean?
2 atoms are joined by a single covalent bond
E.g. Cl2, F2
Does mp and bp increase or decrease down group 7? And why
- increase
- size of molecules increase, more electrons, stronger Van Der Waals
- more energy needed to break intermolecular forces (covalent bond is NOT broken)
Why does volatility decrease down group 7?
Larger the molecule, more energy needed to change physical state
What is volatility?
How easily a substance evaporates
Is there a trend in solubility of group 7 elements in WATER?
No trend
Is there a trend in solubility of group 7 elements in ORGANIC SOLVENTS?
Yes, solubility increases down group
Does reactivity increase or decrease down group 7? And why
Decreases
- atomic radius increases, electron shielding increases, nuclear attraction decreases
What does fluorine look like?
Pale yellow gas
What does chlorine look like?
Pale green gas
What does bromine look like?
Orange liquid
What does iodine look like?
Shiny grey solid, sublimes to violet gas
A halogen is dissolved in water and is brown, what element is it?
Iodine
Give colours of chlorine bromine and iodine dissolved in cyclohexane
Chlorine: pale green
Bromine: orange/brown
Iodine: violet
What is formed when halides react with aqueous silver ions?
A precipitate is formed
Give general equation for Halide + aqueous silver ions
Ag+(aq) + X-(aq) AgX(s)
Give a test for halide ions, and results
- Add nitric acid and silver nitrate ions to sample
- Precipitate should form, white=Cl, cream=Br, pale yellow=I
- Add dilute ammonia, if precipitate dissolves=AgCl
- If not, add conc ammonia, if dissolves=AgBr
- If precipitate not dissolved=AgI
Which is the strongest oxidising agent, Cl or I?
Cl, oxidising ability decreases down group 7
What is a spectator ion?
Ions that are unchanged in a reaction (therefore left out of ionic equations)
Give ionic equation of chlorine and iodide ions
Cl2 + I- 2Cl- + I2
In reactions between halogens and halides, which will become ions?
Strongest oxidising agent
What do half equations show?
Oxidation and reduction of species in an equation
Will there be a reaction between Br2 and I-? If so give colour changes (in cyclohexane)
Yes; Br2 is stronger oxidising agent than I, will become ions
Colour changes from orange to violet
Will there be a reaction between I2 and Cl-? If so give colour changes (in cyclohexane)
No reaction, chloride is stronger oxidising agents, and is already ions
Why is the reaction between a halogen and a halide called a ‘displacement reaction’?
Halogen displaces (pushes out) a less reactive halogen from a compound
