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Energetics Design Lab

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Introduction

Rammy Abssi Chemistry - 11 May 04, 2009 Energetics Planning Lab Research Question: How does the strength of the acid, affect the change in temperature of a reaction with sodium carbonate (acid-base reaction)? Hypothesis: I believe that if acid is stronger, than the change in temperature of the acid-base reaction will be greater. Variables: Type of Variable Variable Range of Values/Method of Control Independent Variable Strength of Acid (Type of Acid) From 0.30g to 1.80g in increments of 0.30g Dependent Variable Change in Temperature Read from thermometer at the peak of reaction Controlled Volume of Acid Used 50cm3 in all trials Initial Temperature All reactions start off at room temperature (21�C - 22�C) The Base Which the Acid is Reacted With Sodium Carbonate Na2CO3 Materials: * Copper cup * Styrofoam cup * Lid for copper cup * Total of 31.80 grams of sodium carbonate (� 0.005g) * 150ml hydrochloric acid (� 0.5ml) [50ml each trial] * 150ml sulfuric acid (� 0.5ml) [50ml each trial] * 150ml ethanoic acid (� 0.5ml) [50ml each trial] * Balance (� 0.005g) * Thermometer (� 0.5�C) * Stirrer Diagram: Method: There will be three trials for each of the three different types of acids. Using 9 weighing boats split the sodium carbonate into 6 sets of 2.65 grams and 3 sets of 5.30 grams. ...read more.

Middle

Hydrochloric Acid: 1 = (x * 50) / 1000 x = 50 / 1000 x = 0.05 There are 2 moles of Hydrochloric Acid 0.05 / 2 = 0.025 0.025 x 106 = 2.65g Ethanoic Acid: There are also two moles, therefore its also 2.65g Sulfuric Acid: There was only one mole of sulfuric acid, therefore the amount of sodium carbonate is 5.30g Hydrochloric: Na2CO3 + 2HCl --> 2NaCl + H2O + CO2 How much heat was evolved? q = mC?T q = (52.65)(4.18)(3.3) q = 726.3J = 0.73kJ How many moles of H+? 1mol HCl = 1 mol H+ ? mol H+ = 1.00 x 0.0500 = 0.0500 mol H+ How much heat/mol H+? ?H (neutralization) = 0.73/0.0500 = -14.6 kJ/mol % Error ((-14.6 - -57.1)/-57.1 ) x 100% = 74.4% Sulfuric: Na2CO3 + H2SO4 --> Na2SO4 + H2O + CO2 How much heat was evolved? q = mC?T q = (55.30)(4.18)(6.5) q = 726.3J = 1.5 kJ How many moles of H+? 1mol H2SO4 = 2 mol H+ ? mol H+ = (1.00 x 0.0500)/2 = 0.025 mol H+ How much heat/mol H+? ?H (neutralization) = 1.5/0.025 = -60.0kJ/mol % Error ((-60 - -57.1)/-57.1 ) x 100% = 5.08% Ethanoic: Na2CO3 + 2CH3COOH --> 2CH3COO-Na+ + H2O + CO2 How much heat was evolved? ...read more.

Conclusion

Another limitation to this experiment is the fact that only one weak acid was used, as compared to two strong acids. Due to the fact that the school did not supply phosphoric acid, only one weak acid was available. This affects the results because the comparisons of weak acids and strong acids become limited to only two comparisons. If phosphoric acid was used than the comparisons between strong acids and weak acids would have been increased to four. All in all, this results in a more accurate conclusion. Looking at the percentage error in these experiments: Hydrochloric Acid: For hydrochloric acid, the percentage error was 77.4% however for the percentage uncertainty it is 59.7%. The percentage error was greater than the percentage uncertainty meaning this is a random error which I made in the experiment. This is most likely due to the heat loss in the experiment. Sulfuric Acid: For sulfuric acid, the percentage error 5.08%, and the percentage uncertainty was 36.8%. This means that the error was a systematic error. The value to of delta H for sulfuric acid in the experiment was very close to the theoretical value of delta H for sulfuric acid. Overall, the percentage errors for these acids were relatively very high. This could be due to the fact that calcium carbonate is a gas releasing base. Therefore, CO2 is released into the environment and a lot of heat is lost. ...read more.

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