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Effect of concentration of the acid&alkali on heat of neutralization

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Introduction

HEAT OF NEUTRALIZATION INTRODUCTION Neutralization of an acid and base is an exothermic process, that is, energy will be liberated. As we do not see any changes to the solution when during the reaction, except for its temperature rising, we can safely assume that most, if not all, of the energy is given off as heat energy. Therefore, when an acid and base is mixed together, it will react and produce energy in the form of heat, and as a result, the temperature of the solution will rise. This rise in temperature can then be measured using a thermometer, and the amount of energy released can be found out using the equation which will be explained below. The list of questions that we have were: 1) How would the concentration of acid and the base reacting affect the heat of neutralisation? 2) How would the strength of acids and bases affect the heat of neutralisation? E.g. Do HCl and NaOH produce more heat when reacted as compared to CH3COOH and NH3 given that the concentrations are the same? ...read more.

Middle

HCl and NaOH Dependent Variable: Amount of heat produced by the reaction Controlled Variable: Volume of the HCl and NaOH mixed together Our rationale of investigation to observe a trend in the relationship between the concentration of acid and base, and the amount of heat produced as a result of the reaction. From this information, we can also deduce the molar heat of neutralization of HCl by NaOH. One possible application of this experiment is to help people who eat antacids. When the base in the antacid neutralizes the acid in our stomach, heat will be produced and the patient will feel heaty. However, if we can find out the molar heat of neutralization, we can advise the patient to drink a certain amount of water to keep their temperature low. MATERIALS AND METHODOLOGY The materials used were the following below: 1. 50ml of each 2.0mol HCl, 2.0mol NaOH 2. 50ml of each 1.0mol HCl, 1.0mol NaOH 3. 50ml of each 0.5mol HCl, 0.5mol NaOH 4. 50ml of each 0.2mol HCl, 0.2mol NaOH. ...read more.

Conclusion

We can also assume that the specific heat capacity and density of the solution to be similar to water, and thus, they would be 4.184J/g and 1.00g/ml respectively. Total mass of water: Approximate temperature change for the concentration of 1mol (derived from graph above): And thus: Also, we used 50ml of 1mol acid and base each. Therefore, the amount of mol of the acid or base will be: Finally we get: CONCLUSION AND DISCUSSION Thus we can conclude that there is linear relationship between the concentration of the acid and base, and the change in temperature of the solution, and that a higher concentration of the acid and base would produce a greater amount of heat when they react together. We can see this as the 2.0mol acid and base caused the solution to rise 13�C in temperature, as compared to the 0.2 mol acid and base, which caused the solution to rise only 2�C in temperature. Finally, we conclude that the molar heat capacity of HCl by NaOH is approximately 52.5kJ/mol from the mathematical equation above. ...read more.

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***
The student has carried out an experiment to investigate the effect of changing concentrations of acids and bases on the heat of neutralization and produced a sensible set of data. The experiment had a stated hypothesis, with clear direction on how this was to be tested. The experimental data was limited by an insufficient range and number of repeats and failure to consider heat loss in the experiment. The report's conclusion is concise but there is no evaluation used to look at laboratory procedures and improvements to the methodology.
Planning
A prediction has been made but it would be helpful to make this quantitative.
A procedure has been planned but it would be preferable to see some attempt to assess hazards.
The range is limited and no repeats were carried out.
A number of key factors were not considered during the planning stage such as limiting heat loss from the containers.
Carrying out the experiment
The results are fairly clearly recorded but there were no repeats and the range was limited.
Analysis
The graph was well presented and the pattern of results was recognized. The data was processed to calculate the heat of neutralization.
Evaluation
Unfortunately there was no evaluation of the procedure.

Marked by teacher Stevie Fleming 01/01/1970

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