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Thermometric titration lab

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Introduction

Samia Murgham 11N Chemistry Lab: Thermometric Titration Aim: to determine the concentration of hydrochloric acid by temperature in a titration. DATA COLLECTION AND PROCESSING Raw Data Collection: Quantitative Results: Trial 1: Burette Reading Total amount HCl added (cm3) Time (seconds) Temperature (�C) 8.3 0 � 0.1cm3 0 � 0.15s 22.5 � 0.1 10.3 2.0 � 0.1cm3 20 � 0.15s 24.5 � 0.1 12.3 4.0 � 0.1cm3 40 � 0.15s 26.4 � 0.1 14.3 6.0 � 0.1cm3 60 � 0.15s 26.7 � 0.1 16.3 8.0 � 0.1cm3 80 � 0.15s 26.6 � 0.1 18.3 10.0 � 0.1cm3 100 � 0.15s 26.5 � 0.1 20.3 12.0 � 0.1cm3 120 � 0.15s 26.4 � 0.1 22.3 14.0 � 0.1cm3 140 � 0.15s 26.1 � 0.1 24.3 16.0 � 0.1cm3 160 � 0.15s 25.7 � 0.1 26.3 18.0 � 0.1cm3 180 � 0.15s 25.2 � 0.1 28.3 20.0 � 0.1cm3 200 � 0.15s 24.8 � 0.1 Trial 2: Burette reading(cm3) Total amount HCl added (cm3) Time (seconds) Temperature (�C) 22.0 0 � 0.1cm3 0 � 0.15s 22.5 � 0.1 24.0 2.0 � 0.1cm3 20 � 0.15s 24.1 � 0.1 26.0 4.0 � 0.1cm3 40 � 0.15s ...read more.

Middle

160 � 0.5s (25.7 +26.5)�2 26.1 � 0.1 18.0 � 0.1cm3 180 � 0.5s (25.2 +26.3)�2 25.8 � 0.1 20.0 � 0.1cm3 200 � 0.5s (24.8 +26.1)�2 25.5 � 0.1 Uncertainties of the experiment: Uncertainty of the 25 cm3 pipette is � 0.1 cm3, and the percentage uncertainty is: 0.1 x 100 = 0.4% 25.0 Percentage uncertainty of the burette since 20 cm3 was used altogether in each trial: 0.1 x 100 = 0.5% 20 Percentage uncertainty of the temperature probe: the temperature rise was 26.8-22.5= 4.3�C. Two readings were taken to measure this and so the uncertainty will be multiplied by 2. [(0.1 / 4.3) x 100] x 2= 4.7% Uncertainty of the stopwatch: (0.5/ 200) x 100 = 0.25% Total percentage uncertainty: 0.25% + 4.7% + 0.5% + 0.4%=5.85% Graph showing the results of the experiment: The equation for the neutralization reaction is: HCl (aq) + NaOH (aq) -->NaCl (aq) + H2O (l) NaOH= (1 x 25)/1000= 0.025 mol of NaOH involved in the reaction Since the ratio that NaOH reacts with HCl is 1:1 then 0.025 mol HCl is required to neutralize the NaOH. ...read more.

Conclusion

* The wrong concentration of NaOH may have been written on the bottle as it was made carelessly. * The HCl concentration of HCl which was used as the 'standard value' that results were compared to may have been inaccurate. * Heat could have been lost to the surroundings from the polystyrene cup. Improvements that can be made to increase the accuracy of this experiment: To combat problems in the first 3 bullet points: the concentrations and purity as well as pH of each chemical can be measured before performing the experiment to ensure that they are accurate and do not affect the results obtained. A calorimeter, a simple device that insulates heat well, can be used instead of a polystyrene cup so that heat loss is prevented. It contains an "insulated jacket" which does not allow any heat to escape or to be absorbed from the surroundings. It also has a stirrer which keeps the heat well and evenly distributed. It has an initiator wire that starts the reaction instead of lighting a wick then moving it under a beaker. The experiment could be repeated more times to improve accuracy by obtaining better averages of many raw data values. ...read more.

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