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Investigation of the carbonate - bicarbonate system

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Introduction

INVESTIGATION OF THE CARBONATE - BICARBONATE SYSTEM (ALKALINITY OF AQUEOUS SYSTEMS) NAME: Leo Chiedu Aim Alkalinity in this experiment can be defined as the measure of the pH buffering capacity in water (e.g. river water, sea water, lakes etc.). This experiment was carried out using a prepared carbonate - bicarbonate solution against hydrochloric acid (0.1M HCl). Titration and pH indicator method was used to determine the equivalence point. The experiment also compares the titration and pH indicator method that is, looking at the option that will give a better approach in determining the equivalence point. Compared the digital and analogue pH meters that were used during the experiment by different groups. The experiment also aims at showing the importance of carbonate - bicarbonate system in environmental chemistry as it affects the natural water system. INTRODUCTION In Nigeria, water pollution is a serious environmental issue as it relates to the oil industries in the Niger Delta region, this can be attributed but not limited to the continuous flaring of fossil fuel. This creates acid rain deposition thus reducing the buffering capacity of rivers and lakes. The major source of living and earning in this area is fishing, but the continuous flaring of gas has resulted in acid precipitation, which has affected fishing. ...read more.

Middle

+ CO3-2(aq) Various results were obtained during the titration and pH indicator methods. Table (1) shows the values obtained when 0.1MHCl was titrated against the carbonate/bicarbonate mixture. Table (2) shows the values for the pH indicator method, table (3) shows the values for the derivative curve and table (4) shows the class result (raw data). The value obtained was then plotted on a graph to obtain various readings; the graphs would be explained later in the discussion. The plot on figure (1) shows the relationship between the pH and volume of 0.1M HCl used. Figure (2) is the derivative curve, figures (3 & 4) is used to determine the equivalence points of the reactions. Furthermore, figures (5 & 6) shows the 95% confidence intervals and standard error (S.E). Using titration method to determine the end points. Phenolphthalein indicator (cm3) Methyl orange indicator (cm3) 2.5 9.5 2.5 9.6 2.6 9.6 Table (1) volume of 0.1MHCl titrated against the carbonate/bicarbonate mixture Calculation (1) Determination of carbonates (CO3-2) levels using the titration and pH indicator methods, values obtained from the table (1) and the derivative curve. CO3-2 + 2HCl H2O + CO2 + 2Cl- (1.1) From the above equation; 1 mole carbonate (CO3-2) = 2 moles HCl step (1) 1 mole 0.1MHCl = 1x 10-4 mole HCl = 1/2 x 10-4 mole CO3-2 step (2) ...read more.

Conclusion

Methyl orange changes from yellow to but this change is not very clear to eye easily. Titration method involves carrying out the process repeatedly so as to get a concordant result, many factors can affect such reading, for instance, sample transfer to beakers will affect the quality of result obtained. However, the pH indicator method gives a more accurate and consistent result when used appropriately. This method gives a wider spread of values compared to titration method. Comparing class values. From the descriptive statistic, it can be seen that the mean values of both meters are not different, therefore, both meters are equal in performance. There is 95% confidence interval that the samples are probably from the source. Conclusion and Recommendation The alkalinity of the water sample was monitored using the titration and pH indicator methods for the determination of equivalence point. The end point value was used to determine the amount of carbonates and bicarbonates present in the water sample. Compared the class results to obtain a 95 % confidence interval that the sample was not from the same source. The following recommendation was made; > Further investigation should be carried out using a different methyl orange indicator, for instance, a mixed bromocresol methyl red indicator > Digital/automatic titrator should be used instead of the manual titration. ...read more.

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