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To determine the amount of ammonia in a sample of household cleaning product, 'cloudy ammonia', in the form of NH4OH through the process of volumetric analysis.

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Introduction

Volumetric Analysis of Ammonia in Household Cleaning Product Aim: To determine the amount of ammonia in a sample of household cleaning product, 'cloudy ammonia', in the form of NH4OH through the process of volumetric analysis. Introduction: Neutralisation refers to the process whereby an acid reacts with a base in stoichiometric proportions to each other to form a salt and water. In this experiment, the neutralisation reaction can be summarized by the following equation: HCl (aq) + NH4OH (aq) NH4Cl (aq) + H2O (l) In this prac, the primary standard is Na2CO3. Primary standards are substances that possess certain properties (i.e. it is soluble), which enable it to be made up into a solution of a known concentration with distilled water to high degree of accuracy. A secondary standard on the other hand, is any solution that has an accurately known concentration. In this experiment, HCl acid is the secondary standard. The standardising of HCl can be summarized by the following equation: 2HCl (aq) + Na2CO3 (aq) 2NaCl(aq) + CO2 (g) + H2O (l) Since sodium carbonate is deliquescent, it is kept in a desiccator to prevent it from absorbing water vapour from the atmosphere. The equivalence point of a titration is the point where the reactants are present in stoichiometric proportions to each other. ...read more.

Middle

Results: Part 1: Preparation of Sodium Carbonate Solution: Calculations: The mass of Na2CO3 required to make up a solution of approx. 0.05M: Number of moles = Concentration Volume = 0.05 .25 = 0.0125 mol. Mass = number of moles molar mass ? m(Na2CO3) = = = 1.325 = 1.33 g Table 1.1: Mass of Substances Substance: Mass: (g) Empty Beaker 33.59 Na2CO3 and Beaker 34.92 Na2CO3 1.33 Part 2: Standardisation of HCl: Table 2.1: Volume of NaCO3 Sample Sample/ Titration Number: Volume (ml) 1 20.0 2 20.0 3 20.0 Average volume of NaCO3 used: 20.0ml Table 2.2: Volume of HCl Titrated Titration Number: 1 2 3 Initial Reading (ml) 0.0 17.1 33.0 Final Reading (ml) 17.1 34.6 50.0 Volume (ml) 17.1 17.5 17.0 Average Volume of Titrated HCl: 17.2ml Calculations: The equation: 2HCl (aq) + Na2CO3 (aq) 2NaCl(aq) + CO2 (g) + H2O (l) We know that the Na2CO3 solution is 0.05M and 20.0ml so: n(Na2CO3) = 0.05 0.02 = 1.0 10^-03 moles From the equation, the ratio of n(HCl) : n(Na2CO3) is 2:1 ? n(HCl) = 1.010^-03 2 = 2.010^-03 moles Concentration (c) = Number of moles (n) Volume (L) ? c(HCl) = = 0.116M Part 3: Analysis of 'Cloudy Ammonia': Table 3.1: Volume of 'Cloudy Ammonia' Sample Sample/ Titration Number: Volume (ml) 1 20.0 2 20.0 3 20.0 Average volume of 'Cloudy Ammonia' used: 20.0ml Table 3.2: Volume of HCl Titrated Titration Number: 1 2 3 Initial Reading (ml) ...read more.

Conclusion

A stopper will keep losses of the ammonia to a minium, thus retaining the accurate number of moles of ammonia required in the titration process. Ammonia vapour may irritate the skin, eyes and respiratory system, thus the lab must be well ventilated, safety glasses worn and the ammonia stoppered to minimise the hazards. 3. A few years ago, the bottles were labelled '2.5% w/w ammonia as NH3', however the labels have now been changed to '5% w/w ammonia as NH4OH'. The change is probably due to the fact that the manufacturers have added water to their products. Although this causes the ammonia to be less concentrated, the new weight is heavier than the old weight by two times due to the fact that ammonia has been ionised by the water molecules. This is best summarized in the equation: NH3 (aq) + H2O (l) NH4+(aq) + OH- (aq) It is possible that the manufacturers made such a change in their product for commercial purposes. To an ordinary consumer with no chemistry background, the change would probably mean to them that they are receiving more value for their money, whereas in actual fact, they are still getting the same amount of ammonia. Conclusion: In conclusion, it may be generalised that volumetric analysis is a fairly accurate method of analysing the amount of ammonia as NH4OH present in a sample of 'cloudy ammonia' and that the actual yield of ammonia will vary to the theoretical yield of the manufacturer due to various experimental inconsistencies and errors. ...read more.

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5 star(s)

A five star piece of work. Excellent introduction shows a clear understanding of titration and shows good balanced equations. The procedures are excellent and the results show accuracy and lots of skill. Excellent calculations used and analysis of results.

Marked by teacher Patricia McHugh 08/04/2013

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