ES Flashcards
How do you calculate atom economy?
Mr of useful products/ total Mr of products x 100
What forms at the anode if the solution contains halide ions?
Halogen
What happens at the anode if it’s a sulphate or nitrate?
Oxygen is produced
What happens at the anode if its a hydroxide?
Oxygen produced from OH-
What is formed at the cathode if it is a group 1/2 metal or aluminium?
Hydrogen gas produced from water
What is produced at cathode if it’s a metal not in group 1 or 2 or aluminium?
Metal produced
What is produced at the cathode if it’s an acid?
Hydrogen from H+ ions
Define oxidation
Loss of electrons
Define reduction
Gain of electrons
What are the two steps of a iodine-thiosulfate titration?
Use an oxidising agent to oxidise as much iodine as possible
- excess acidic potassium iodide
Titration iodine with sodium thiosulfste to calculate moles of iodine produced
then calculate concentration of oxidising agent from this
What is the appearance of fluorine at room temp?
Pale yellow gas
What is the appearance of chlorine at room temp?
yellow-Green gas
What is the appearance of bromine at room temp?
Dark red volatile liquid
What is the appearance of iodine at room temp?
Shiny black solid
What is the trend in volatility of halogens? why?
Decrease down group
the strength of the IDID intermolecular bonds inceeases down group due to more electrons
What is the trend in solubility of halogens in water?
Decreases in solubility down group
Colour of chlorine in water?
Pale green
Colour of bromine in aqueous solution?
yellow/Orange
Colour of iodine in aqueous solution?
Brown
Are halogens more or less soluble in organic solvents than water?
More
Colour of chlorine in hexane?
Pale green
Colour of bromine in hexane?
Orange/brown
Colour of iodine in hexane?
Violet
Trend in reactivity of halogens? And 2 reasons?
Decrease in reactivity
Less shielding at top
So stronger attraction to extra electrons from nucleus
How do you prepare HCl?
Add sulfuric acid or phosphoric acid to chlorine ions
How do you prepare HBr and HI?
Add concentrated phosphoric acid to NaI/Br
Trend in thermal stability of hydrogen halides
Decreases down group as bond strength decreases due to shielding
Acidity of halogen halides?
All strong acids apart from HF which is a weak acid
Reaction of hydrogen halides with ammonia?
Produce ammonium halide -> white fumes
Reactions of hydrogen halides with sulfuric acid?
HCl- no reaction
HBr- SO2
HI- H2S
what are properties of dynamic equilibrium?
must be a closed system
rate of forwards reaction = rate of backwards reaction
concentrations are constant
Kc>>1 kc> 1 kc=1 kc<1 kc<<1
reaction appears to have gone to completion - equilibrium lies far to the right
more products than reactants - equilibrium lies far to the right
equilibrium is in he centre
more reactants than products - equilibrium is to the left
reaction appears to not have happened - equilibrium lies far to the left
effect on Kc of
pressure
temperature
concentration of a reactant
changes Kc
changes Kc
no effect on Kc
why doesn’t changing the concentration of a reactant change the Kc
if a concentration term on the top becomes larger one on the bottom must also become larger to keep Kc constant so equilibrium position moves to left etc
what are the uses of chlorine?
sterilising water by killing bacteria
bleaching
what are the risks associated with storing and transporting chlorine?
it is toxic and corrosive - keep away from eyes and skin and when breathed in irritates respiratory system
is an oxidising agent so needs to be kept away from flamable materials
needs to be stored under pressure in small cylinders
what is the solubility of
Ag Cl
AgBr
AgI
with ammonia?
soluble in dilute and concentrated ammonia
soluble in concentrated ammonia
ppt does not dissolve
Describe the trends in the halogens.
Down the group: darker in colour, melting and boiling points increase, less volatile, more soluble.
Most reactive non-metals.
All diatomic.
Single covalent bonds.
Describe halide reactions with silver
Silver chloride is white
Silver bromide is cream
Silver iodide is yellow
Describe the production of bromine.
Chlorine is added to acidified sea water to displace bromine ions. Bromine vapour and water are given off. Vapours are condensed, forming two layers. Impure bromine is distilled and dried. Dense bromine is run off.
Describe the electrolysis of brine.
Forms chlorine, hydrogen and sodium hydroxide.
Anode: 2Cl- > Cl2 + 2e-.
Cathode: 2H2O + 2e- > 2OH- + H2.
Overall: 2Cl- + 2H2O > Cl2 + 2OH- + H2.
Describe the electrolysis of a molten compound.
Solid ionic compounds don’t conduct electricity. If this compound is melted, charged ions are free to move and carry a current.
Cations go to the cathode. Produces a metal.
Anions go to the anode. Produces a non-metal.
Describe the electrolysis of solution.
Water can be reduced at the cathode or oxidised at the anode.
At the cathode: metal ions from the salt + water. More reactive metals remain as ions and hydrogen. Less reactive metals are played onto the cathode.
At the anode: negative ions from the salt + water. Halides produce the halogen.
Other negative ions produce oxygen.
Describe chlorine transportation.
Chlorine is transported as a pressurised liquid in a fixed volume. Able to vent some chlorine as a gasm
The routine check involved soaking a cloth in concentrated ammonia solution. If there is a leak, a white cloud of ammonium chloride is produced
What effect does chlorine have?
Irritates eyes, skin and respiratory system.
Reacts in the lungs to form hydrochloric acid.
Describe the Deacon process.
4HCl + O2 <> 2Cl2 + 2H2O.
Passed over a catalyst.
High pressure, low temperature, excess oxygen.
Production of PVC:
CH2=CH2 + Cl2 > CH2ClCH2Cl.
CH2ClCH2Cl > CH2=CHCl + HCl.
Describe the effect of changing concentrations on equilibrium.
Increasing reactants goes to products.
Increasing products goes to reactants.
Decreasing reactants goes to reactants.
Decreasing products goes to products.
Describe the effects of changing pressures on equilibrium.
Increase goes to the side of fewer gas moles.
Decrease goes to the side of more gas moles.
Describe the effects of changing temperature on equilibrium.
Heating favours the endothermic reaction.
Cooling favours the exothermic reaction.
