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An Experiment to determine What Factors Affect Neutralisation of 25cm Sodium Hydroxide

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Introduction

An Experiment to determine What Factors Affect Neutralisation of 25cm� Sodium Hydroxide Introduction Neutralisation is the reaction between an acid and an alkali that produces a neutral solution - a solution neither acidic nor alkaline. During the reaction, the acid dissociates and produces hydrogen ions, H+, and the alkali dissociates and produces hydroxide ions, OH-. If the number of H+ ions are equal to the number of OH- ions, then neutralisation occurs because there are no extra ions from either the acid or alkali to make it an acidic or alkaline solution - This neutral solution is water: H + OH = H2O. A salt is also produced, depending on what type of acid and alkali you use. The factors that affect neutralisation: - The concentration of the acid - The strength of the acid - The strength of the alkali - The temperature Preliminary Investigation We carried out a preliminary experiment to find the best conditions to carry out an investigation to determine how concentration affects the volume of acid needed to neutralise an alkali. We took three different acids and three different alkalis and tested the volume each solution needed to neutralise either Hydrochloric acid or Sodium Hydroxide. We kept all the concentration of the reactants the same, so the tests would be fair, and the three acids were tested with 20ml of 1M Sodium Hydroxide, while the three alkalis were tested with 20ml of 1M Hydrochloric acid. ...read more.

Middle

Method: 25ml of 1M Sodium Hydroxide will be safely pipetted into a conical flask. This will then be placed onto a white tile underneath a burette filled with Hydrochloric acid. Phenolphthalein indictor will then be added to the alkali. The reading on the burette will be noted down, and then the acid will be run into the alkali and indicator solution. The conical flask will be agitated constantly so the acid and alkali are mixed together thoroughly, and when the indicator changes colour, the acid is stopped running and the volume of acid will be noted down. Each test will be repeated three times for each different concentration of acid, and we will use five different concentrations of acid. Diagram: Apparatus: Hydrochloric Acid of 1.0M, 1.25M, 1.5M, 1.75M and 2.0M Sodium Hydroxide Phenolphthalein Burette Burette filler Conical Flask Pipette Safety bulb White Tile Results These results show the readings on the burette at the start and at the end of the main experiment: Concentration (M) Volume of Acid (ml) Trial 1 Trial 2 Trial 3 Start End Start End Start End 1.0 0.2 25.2 0.5 25.6 0.6 22.0 1.25 0.5 22.3 22.3 44.2 1.2 24.0 1.5 0.2 18.9 18.9 37.7 0.4 19.1 1.75 1.3 16.9 16.9 32.4 32.4 48.1 2.0 1.2 13.7 13.7 26.3 26.3 38.4 Trial 3 for the1.0M acid looked incorrect compared to trials 1 and 2, so we decided to carry it out again: Concentration (M) ...read more.

Conclusion

This would have affected our final results, but we noticed the error and carried out another trial to replace the anomalous one, and this provided sufficient evidence to support my conclusion. Even though this investigation did produce a reliable set of results, we could improve this experiment by using a pH meter and an electronic burette. A pH meter is a device that measures the exact moment a solution becomes neutralised. An electronic burette pours 1ml of the solution inside it every second. agitating the solution could obviously not move at the exact same speed for every separate test carried out, our results could be slightly unfair and inaccurate. By using a machine the experiment would not be affected by human error thus making the experiment more accurate and even fairer. We could also investigate the factor, strength. Strength is the amount of ions free in a solution. If a solution is strong then more ions are free to react. In a weak solution there are some ions that are not free to react. For such an experiment, we could use different strengths of acid to find out how the volume of acid needed for neutralisation is affected by strength. The experiment would be very similar to the investigation we have just conducted, but it will allow us to find out the relationship between volume of acid and strength, and see if it is the same as the relationship between the volume of acid and concentration. ...read more.

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