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To observe how concentration affects the temperature of neutralization.

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Introduction

Investigation: Heat of Neutralization Aim To observe how concentration affects the temperature of neutralization. Background Knowledge Acids and alkalis are opposites. If they are mixed together in the right proportions, they are cancelled out. The acidity and the alkalinity of the substances are destroyed. This is a neutralisation reaction. Two new compounds are formed in a neutralization reaction - a salt compound and water. The name of the salt depends on the alkali metal and the acid used. The acid and alkali must be in exactly equal amounts to get a perfect neutral solution. The neutralisation is an exothermic reaction because it gives out heat energy, making the temperature rise. An acid is a substance that dissolves in water, producing H+ ions. A strong acid (about pH1) produces a high concentration of H+ ions in a water solution. An example is Hydrochloric Acid. An alkali is a soluble base (an alkali that reacts with an acid to form salts), producing OH- ions in a water solution. A strong alkali (about pH14) ...read more.

Middle

This process makes calcium sulphate which can be sold to make plaster. Prediction I predict that as the concentration of the acid and alkali in increased, the temperature will also increase when neutralisation occurs. This is because neutralisation reactions are also exothermic reactions. They will be giving out heat energy. Method Set up equipment (see diagram below). Measure 0.1 mol dm-3 of both Hydrochloric Acid and Sodium Hydroxide and put them on separate measuring cylinders. To make measuring easier, use three burettes - one for the Hydrochloric Acid, one for the Sodium Hydroxide and one for the water. Mix them together onto a test tube and record the temperature. Repeat the experiment for 0.2 mol dm-3 of Hydrochloric Acid and Sodium Hydroxide up to a concentration of 1 mol dm-3. The input variables in the experiment are: * The concentration of the acid. * The concentration of the alkali. The output variables are: * The change in temperature. ...read more.

Conclusion

The temperature increases by about 0.5OC each time the concentration is increased by 0.1 mol dm-3. An anomaly was when the concentration was 0.9 mol dm-3, the average temperature did not increase. Evaluation The experiment is successful as a pattern could be seen from the graph. The equipment was washed every time to ensure there were no solutions left. The same volume of chemicals was put in each time. If a digital thermometer was used, the temperatures could be more accurate. If I had used a wider range of concentrations for the acid and alkali - such as 0.5, 1, 1.5 and 2 mol dm-3, I would have got bigger differences for the concentrations. On my experiment, the concentrations go up by 0.1 mol dm-3 every time and therefore, there aren't any big differences in the results. If I had more time to do my experiment, I would have made this change. To make the experiment better, I will use a bigger scale next time. ...read more.

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