The halogens and atom economy

• Silver ions and halide ions react to form a precipitate.

• Dilute nitric acid should be added to first to remove other ions which may interfere with the reaction.

• Depending on the halide ion, the colour of the precipitate will be different.

• The precipitates can look quite similar, so to aid identification, ammonia solution is added.

Risks of storing and transporting chlorine

• Chlorine is toxic and corrosive so it should be kept away from the skin and eyes.

• It also irritates the respiratory system, so inhalation should be prevented.

• Chlorine is an oxidising agent so should also be kept away from flammable objects

• To minimise the risks associated with chlorine, it is stored and transported as a liquid under pressure in small cylinders

Uses of chlorine

• Sterilises water making it safe to drink and swim in.

• Kills disease causing microorganisms

• Used to make bleach

Atom economy

• Atom economy is a measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical equation

• % atom economy = (molecular mass of desired product / sum of molecular mass of all products) x 100

• Generally reactions with high atom economies are better because they produce less waste making them cheaper and more environmentally friendly.