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An investigation into the variables that effect energy changes during a neutralisation reaction.

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Introduction

Nazreen Deller Chemistry Coursework 12/10/02 Aim : An investigation into the variables that effect energy changes during a neutralisation reaction. Background information : A neutralisation reaction is a process whereby the acidity or alkalinity of a substance is destroyed. In order to make a neutral substance you must first determine the ph of the substance, one you have determined whether it is alkali or acid you can then add the same mount of alkali if the substance is acid. This will remove H+ (aq) ions. If the substance is an alkali then you must add the same amount of acid, removing the OH- (aq) ions. It is important that the acid and alkali particles are exactly equal to get a neutral solution. When two chemicals are neutralised, a reaction occurs. This reaction normally results in an event called 'energy change'. An energy change is normally the discharge of energy lost in a reaction. There are two types of energy change If a bond is broken during a reaction, energy is needed , so the surroundings lose heat and reactants gain energy in the form of heat to carry out this action this is carried out through an Endothermic energy change. ...read more.

Middle

The equation of this reaction is : HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l) Examples of Neutralisation in everyday life. * Bee sting : This is acidic. It can be neutralised by bicarbonate of soda. * Wasp sting : Unlike the bee sting this is alkaline and can be neutralised by vinegar. * Indigestion : when there is too much acid build up in the stomach. It can be neutralised by an alkaline tablet. Apparatus : * 2 Burettes * 2 Stand and clamp * Funnel * 2 Beakers * Hydrochloric acid * Sodium hydroxide * Distilled water * Universal indicator * Materials and lids for insulation (lids with holes in to fit a thermometer.) * Thermometer. Variables : We will carry out the experiment 6 times with different concentrations of the reactants which are hydrochloric acid and distilled water. Safety: * Safety goggles must be worn when using chemicals and at all times during the experiment. * If any of the chemicals come in contact with skin or clothing it should be rinsed of immediately as they can be irritant or corrosive. ...read more.

Conclusion

Prediction : I predict that the more water and less acid is introduced into the solution will make it weaker and I think that this will slow down the reaction and it will cause less rise in heat. Results Table : Hydrochloric Acid (ml) Distilled Water (ml) Sodium Hydroxide (ml) Temperature Before (degrees C) Temperature After (degrees C) Difference (degrees C) 25 0 25 19 28 9 20 5 25 18 27 9 15 10 25 17 25 8 10 15 25 16 23 7 5 20 25 16 20 4 0 25 25 15 17 2 Conclusion: As less acid and more water is introduced to the sodium hydroxide the temperature decreases as does the difference in temperature. When a solution is neutralised it takes part in an endothermic energy change, this means that the solution gives out heat if the reaction is more violent then there will be more heat produced. The results as I predicted should go down in temperature as the hydrochloric acid is decreased and the water is increased. Evaluation: My results have been conclusive to scientific evidence and my prediction. If I could re- do the experiment I would use better insulation and better measuring equipment. ...read more.

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