Risk Assessment 334a2g

Risk Assessment Before any experimentation can begin it is important to highlight all risks that could develop and put precautions in place to prevent any incidents occurring. The practical methods involved within this investigation are relatively safe as it involves simply timing the reaction. The potential risks are largely due to the chemicals used in the reaction.  Hydrogen peroxide (reactant) Concentration before dilution: (100 volume) Hazards: Corrosive – causes burns to skin eyes and respiratory tract. Harmful if swallowed or inhaled Oxidising agent – with other material may cause fire Concentration in standard solution: 0.1 mol dm-3 (approx 1 vol) Hazards: low risk unless swallowed/ gets into eyes  Solid Sodium Thiosulphate, sodium ethanoate and potassium iodide (reactants) The above are provided in solid salt form: they present low risk unless swallowed. Concentrations in standard solution: 0.005, 0.01 and 0.1 mol dm-3 respectively again the reactants pose a very low risk unless ingested or come into with eyes etc.  Ethanoic acid (reactant) Concentration before dilution: 17.5 mol dm-3 (glacial) Hazards: Corrosive – vapour irritates lungs, causes skin/ eye damage Concentration in standard solution: 2 mol dm-3 Hazards: low risk unless swallowed/ gets into eyes.  Sulphuric acid (reactant) Concentration before dilution: 18.4 mol dm-3 Hazards: extremely corrosive, with skin or eyes can cause permanent damage, dissolution of sulphuric in water is highly exothermic. In some cases could cause water to boil. Concentration in standard solution: 1 mol dm-3 Hazards: May cause skin irritation, harmful if swallowed.  Iodine (product) Iodine can be harmful, and therefore pose a risk in high concentrations however in this investigation only small amounts will be produced. Therefore the low concentration has no serious risks unless it comes into with eyes or is swallowed. A further risk is posed by Sulphur and Sulphur dioxide; these are not reactants or products of the overall reaction however they are produced in the following side reaction. (Sodium Thiosulphate with acids) [17]  S2O32- (aq) + 2H+ (aq) → S(s) + SO2 (g) + H2O (l) Sulphur dioxide is a toxic gas which could pose a serious risk however the reaction of the sodium thiosulphate with the acid is slower than the Harcourt-Essen reaction so the small amount produced in the time taken for the solution to change colour can be deemed insignificant. Furthermore I will keep the acid and the sodium Thiosulphate separate until the reaction commences to prevent any build up of Sulphur dioxide which is corrosive in moist environments. It will not be a risk after the blue colour has appeared as this shows all the sodium Thiosulphate has reacted meaning there will be none available to produce sulphur or sulphur dioxide.

Through conducting this risk assessment it has been discovered that the most dangerous element of the investigation is most likely to be preparing the standard solutions as this is when the chemicals will be present in their most concentrated form. Of these the Ethanoic acid and hydrogen peroxide pose the greatest risk. By the ALARA principle the standard solutions requiring these chemicals will be prepared in a fume cupboard to prevent inhalation of the Ethanoic acid vapour. Gloves will also be required in order to prevent any irritation that may be caused by the hydrogen peroxide and to protect my hands form the corrosive effects of the acid. In making the solutions the concentrated chemicals will be added to water and not vice versa to minimise the exothermic effects. After the standard solutions are made the concentrations of both chemicals remain at safe levels for the duration of the experiment. Additional care will also be required when handling glassware, particularly if it is delicate such as pipettes as there is a risk of shattering creating sharp edges which could cause injury. As per normal laboratory practice safety goggles and lab coats must be worn at all times, with any spillages or breakages being reported immediately.