Elements from the Sea Flashcards
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 and ammonia.
Silver chloride is white and soluble.
Silver bromide is cream and partially soluble.
Silver iodide is yellow and insoluble.
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.
What is assumed for dynamic equilibrium to occur?
Concentrations stay constant.
Forward and reverse reactions are both happening.
The rate of the forward reaction and the backward reaction are equal.
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.
