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Energy conversion in a neutralisation reaction

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Introduction

Energy conversion in a neutralisation reaction Aim We are trying to find out what factors affect the energy conversion in a neutralisation reaction. Variables The variables that can be changed are Concentration of acid Type of Acid Concentration of alkali We choose type of acid Prediction I predict that if the acid is stronger (has a lower pH) than more heat will be given out in the endothermic reaction. Theory Strong and Weak Acids- Acid is an H+donor and a consequence of this is that, in aqueous solutions, acid donates H+ to water molecules to produce oxonium ions H3O+. The presence of oxonium ions gives rise to the familiar acidic properties of all aqueous solutions of acids. Acids vary in strength. Different acids donate H+ to differing extents. Strong acids have a strong tendency to donate H+: the donation of H+ is essentially complete. The reaction with water can be regarded as going to completion and can be described by the following equation, where HA represents the strong acid. ...read more.

Middle

We then put some universal indicator in each beaker and recorded the pH. Then we put a thermometer in one of the beakers with sodium hydroxide in it and added 25 ml of acid to it. Then we observed the thermometer until the maximum the temperature was reached and noted down the result and also noted down the new pH. We then did this two more times for the same acid, after which we changed the acid and did the same for the new acid. We did this for each of the five acids, with two repeats for each acid. Throughout the experiment we wore safety spectacles. Results Acid Starting Temperature (oC) Ending Temperature (oC) Repeat Repeat 1 2 3 1 2 3 Hydrochloric Acid 21.0 20.5 19.8 32.9 32.5 32.4 Sulphuric Acid 21.0 21.0 20.9 32.4 32.8 32.8 Nitric Acid 20.5 21.0 20.8 31.2 32.0 31.5 Acetic Acid 20.9 20.8 20.8 29.9 30.0 29.6 Phosphoric Acid 20.5 21.0 20.8 29.9 30.5 30.1 Acid Average Starting Temperature (oC) ...read more.

Conclusion

It would be impossible to record to over one decimal place; even one decimal place is a slight estimate. Also it was hard to know when the maximum temperature would arise. You had to watch until the temperature started going down and the record the maximum temperature. Even though the results would not wholly accurate, the results came out as expected and agree perfectly with scientific theory so think this is evidence enough to make a firm conclusion that the lower the pH of an acid, the greater the energy conversion in a neutralisation reaction. If I were to do a further investigation it would be to find out if the same applies to alkalis in a neutralisation reaction. So, if the alkali in the reaction has a higher pH, the energy conversation is greater. To do this I would do the experiment the same, except I would choose an acid to keep the same though preliminary work and vary the alkali, instead of the acid. My prediction would be that as the pH of the alkali increased, the energy conversation would increase. ...read more.

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