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Determination of the purity of Sodium Carbonate

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Determination of the purity of Sodium Carbonate Aim: To determine the percentage purity of a sample of sodium carbonate. Equation: Na2CO3 + 2HCl --> 2NaCl + H20 + CO2 Sodium Hydrochloric Sodium Water Carbon Carbonate Acid Chloride Dioxide Chemicals: * 4.00 g dm-3 of impure Sodium Carbonate in solution * 1.00 mol dm-3 Hydrochloric acid Apparatus: * 50cm3 burette burette clamp and stand * 25cm3 bulb pipette pipette pump * Teat pipette * Conical flask white tile * 250cm3 graduated flask * 1 beaker for waste funnel * Methyl Orange indicator * Distilled water Method: To determine the percentage purity of a sample of impure sodium carbonate we must first find out how much, in volume, hydrochloric acid it takes to neutralise the solution (this is an acid and base titration and will need an indicator). To do this I will need to adhere to the following method; 1. Clamp the burette carefully. Fill the burette with the hydrochloric acid using the funnel. Remove the air space below the tap and use the wastage beaker to catch any of the acid. ...read more.


I should use a burette to add an accurate volume of hydrochloric acid to the graduated flask, and when filling up the flask a teat pipette should be used when making up the final few cm3 of the solution. Risk analysis: There is little risk involved in this experiment as all the solutions used are very dilute and are unlikely to harm anyone if spilled. However, for safety measures, a lab-coat and goggles should be worn and extra care should be taken when using the glassware. Error Analysis: The following table shows the error that can occur when reading off the measuring device. I must take these into consideration for my experiment as it could affect my results. Volume / cm3 Error / cm3 Error per cent / % Graduated flask 250 � 0.20 0.08 Bulb pipette 25 � 0.06 0.24 Burette 20 � 0.10 0.50 Pipette 2.5 � 0.04 0.16 The error taken for the burette is as such because I am taking a reading from it twice (initial and final reading), but I am reading to the nearest 0.05cm3 to give a greater degree of accuracy. ...read more.


From the average titration volume I will be able to calculate the percentage purity of the sodium carbonate solution. Moles HCl = Average HCl used x concentration HCl 1000 = 16.65 x 0.08 1000 = 0.00132 Moles Na2CO3 = moles HCl 2 = 0.00066 Moles Na2CO3 = Volume x Concentration 1000 Concentration Na2CO3= Moles Na2CO3 x1000 Volume = 0.00066 x 1000 250 Percentage purity of = Concentration Na2CO3 x RFM Na2CO3 = 0.0264x 106 = 0.27984 Moles HCl = 16.65x 0.08 1000 ? Moles Na2CO3 = 16.65 x 0.08 in 25cm3 1000 x 2 ? Moles in 250 cm3 = 16.65 x 0.08 x 10 1000 x 2 ? Mass Na2CO3 = 16.65 x 0.08 x 10 x 106 in 250 cm3 1000 x 2 = 0.70596 ?Percentage purity = 70.596% of Na2CO3 I now need to take into account the errors that could have been made. Overall percentage = 0.50 + 0.24 +0.08 + 0.16 + 0.60 = 1.58% error So there is a possible error in my percentage purity of 1.58%, Possible percentage = 70.596 ? 1.58 x 100 purity of Na2CO3 70.596 with error = 73.2% to 68.4% Therefore the percentage purity of the sodium carbonate solution could range from the upper bound of 73.2%, to the lower bound of 68.4%. ...read more.

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