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An Investigation into the Heat of Neutralisation

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Introduction

An Investigation into the Heat of Neutralisation Planning: Aim: the aim of this investigation is to look at what effect concentration has on the temperature and energy changes in a neutralisation reaction. Introduction: Neutralisation occurs when an acid and an alkali base are reacted together to form a neutral solution. Despite this, a neutral solution will only be achieved if the alkali and acid are of equal strength. This occurs because the H+ ion in the acid reacts with the OH� ion in the alkali to form H20 or water, which is neutral. The H+ ions are destroyed when they are reacted with a carbonate or metal base. The OH� ions are destroyed when they are reacted with an acid. The equation for this is shown as follows: H+ + OH� H20 However alkalis and acids all differ because of their structure. This means that as well as water being produced, so is a salt. Acid + Alkali Salt + Water XH+ + YOH� XY + H20 HCl + NaOH NaCl + H20 Neutralisation is always an exothermic reaction, therefore heat is given out, because the energy released from forming bonds is greater then that taken in and used in the breaking of the bonds. ...read more.

Middle

4. Record the temperature of the alkali. 5. Measure out 25cm3 of HCl using the second measuring cylinder and pipette. 6. Record the temperature of the acid. 7. Pour the acid into the cup along with the NaOH and very quickly place on the lid. 8. Stir the solution five times with the thermometer. 9. Wait until the temperature has reached its highest point, i.e. when there are no signs it will increase, and then record it. 10. Wash out the measuring cylinders, thermometer and cup then repeat the experiment twice more. 11. Repeat the whole experiment to obtain results for the different combinations of acids and alkalis shown above. When completing the results table below, the initial temperature is the average of the initial temperature of acid and that of the alkali. Results: HCl (hydrochloric acid) CH3COOH ( ethanoic acid) CH3CH2COOH (propanoic acid) NaOH (sodium hydroxide) Initial temp 0C Final temp 0C Temp change 0C 1 2 3 1 2 3 1 2 3 22.1 22.2 22.3 23.4 23.3 23.9 25.1 23.8 23.5 28.8 28.8 28.9 29.7 29.4 30.3 31.3 28.3 27.9 6.9 7.0 7.0 6.3 6.1 6.4 6.2 6.5 6.4 NH4OH (ammonia solution) ...read more.

Conclusion

Although heat was lost to the surroundings, it was lost in all my experiments equally. If I were to redo the experiment there are a few improvements I would make. I feel that I could have been more accurate in measuring my volumes of acid and alkali, but then flaws in my readings could be attributed to human error. Also, because of human error the readings on the thermometer may not have been accurate, however, using a thermometer connected to a computer and having the computer take the readings could solve this problem. Repeating my experiment another time for each of the reactions would be more accurate as I would have more data. If repeating the experiment I would insulate the lid of the cup and the measuring cylinders to prevent heat loss through them. To extend the investigation I could also look at some of the variables that I mentioned above. If I were to investigate a wider range of acids and alkalis it would extend the investigation and enhance my results. Another extension would be to experiment with different concentrations and seeing how they affect the heat of neutralisation, however this was not possible due to time limitations. Laura Davies Chemistry Coursework ...read more.

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