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Exothermic neutralisation reaction.

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Introduction

Exothermic Neutralisation Reaction. Introduction. The aim of this investigation is to try to find out how concentration can effect an exothermic neutralisation reaction. I will be reacting sodium hydroxide with hydrochloric acid, which neutralises to form sodium chloride a salt with water. Sodium hydroxide is an alkali and hydrochloric acid in an acid so therefore when reacted together neutralisation occurs. In this case when both substances are reacted, thermal energy is produced hence an exothermic reaction as thermal energy is radiated out. The reaction will look like this: NaOH + HCl H2O + NaCl The factors that might affect the results of this experiment are: 1. Volume 2. Concentration 3. Type of substance used. 4. Catalyst 5. Pressure Volume can affect the experiment because if it is not kept constant them results will be varied and there would be no proof that concentration can effect this exothermic neutralisation reaction, as the test would not be fair. Also if substances used were different this could affect the end result produced in this case a salt and water, as more reactive acids and alkalis can perhaps can produce a more vigorous reaction and therefore a higher temperature rise as more thermal energy is produced. The input variable that I will change will be concentration. Concentration increases the number of collisions because there are more particles in the solution to collide with each other. So if a solution is more concentrated more particles are bumping into each other. ...read more.

Middle

The aim of this experiment is to find out if it will make a difference which way the neutralisation reactions occurs. When using 1mol/l I will use 10ml of acid/alkali with 10ml of deionised water in order to create a 1mol/l solution with 20ml volume. NaOH HCl Temperature rise 1mol/l 2mol/l 4oC 2mol/l 1mol/l 4oC As you can see it makes no difference if the acid is added to the alkali or the alkali to acid. I have decided to add acid to alkali as instead of using a measuring cylinder, which was stated in the method I would measure the acid using a burette. But this is not possible to do with the alkali as it blocks the burette and sediments are left behind as the solution separates. Preliminary experiment three. The third preliminary experiment will help determine whether I will be able to test very small concentrations of the acid with the 2mol/l concentration of alkali, this will also help me find a range to work in from my results. NaOH HCl H2O Temperature rise 2mol/l 20ml 2ml 18ml 1oC As there was a temperature rise at 0.2mol/l I will measure my results from 2mol/l to 0.2mol/l. There would be no point in going to 0.1mol/l as there degree of temperature would not be readable on the thermometer that I will be using. This will provide me with ten results, which I will have two sets of so that I can compare temperature rise and use the average to plot a graph and see if there are any patterns occurring in the results. ...read more.

Conclusion

If I were to do the experiment again I would test concentrations above 2mol/l to prove my prediction correct beyond doubt. I would predict that after 2mol/l of acid instead of there being OH- ions left in the solution there will be H+ ions left from the excess HCl. This will change the shape of the graph as it will no longer increase but decrease as no more complete neutralisation will occur. This means the graph will level off and produce the same temperature rise as 2mol/l concentration of each. I could further the testing by after reacting each different molar concentration of HCl with NaOH I would test it with litmus paper. This will enable me to show whether complete neutralisation has occurred. If it has occurred then the litmus paper would turn green, if not then an acidic solution would turn red and alkali purple. To further the idea of my prediction I could use a different acid for example sulphuric acid (H2SO4). Sulphuric acid has two hydrogen bonds compared to HCl. Therefore instead of getting a bigger temperature rise at 2mol/l of each you would get it at 1mol/l of acid and 2mol/l of alkali. This is because of the two hydrogen bonds, so at 1mol/l there is the same amount of hydrogen bonds as the alkali. Overall I am pleased with the results that I obtained as they agreed with my prediction that 2 molar concentrations of acid and alkali would produce complete neutralisation and therefore the biggest temperature rise. This is due to the most formation of water, when it occurs the bonds release thermal energy producing the exothermic reaction causing the temperature rise. By Amareen Bhambra 11B. ...read more.

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