Hey,
The question was four marks so it probably needed two/three positives and two/three negatives:
The benefits are:
- It saves lives in smoke detectors
- It emits alpha and low energy gamma radiation that is virtually harmless
- It has a long half-life (of like 430 years) so it won't need replacing
The negatives are:
- It is made from radioactive and reactive plutonium so manufacturers need to utilise protection to avoid exposure to radiation
- It is harmful in its soluble form (but this hardly occurs)
For the shipwrecks question, if investigating oxygen concentration on corrosion, it would probably be best to use the same kind of water with the same kind of nail in the same volume of water in test tubes, but the water should be prepared by:
- Oxygenating it by placing it on a magnetic stirrer for a few hours then pouring it over the nail
- Just using plain tap water; and
- Boiling water and sealing it with parraffin wax or oil
Record results every few days classing rust on a scale of 1 to 5.
Alternatively, you could add ferroxyl indicator which is made of potassium ferricyanide and phenolphthalein that turns blue in the presence of Fe2+ ions as the iron undergoes oxidation, and pink when OH- ions form when water is reduced, but this could interfere with the experiment.
) in brackets so I hope I still get the mark...assuming that's right <_<
