Chemistry Investigation on neutralisation reaction.

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Chemistry Investigation on neutralisation reaction


Neutralisation is the reaction that occurs when an acid has its acidity, that is its hydrogen ions removed by, another chemical containing OH- hydroxide ions. Chemicals that can cancel out an acid in this way are: bases (metal oxides or hydroxides), alkalis (bases that dissolve), metals (e.g. magnesium) or metal carbonates (e.g. marble chips) All of these have a similar way of removing the hydrogen from the acids (they swap it or their metal atoms) but the reactions are quite different. They will all get quite hot if the acid is strong enough, but only the last two will make bubbles. Metals form hydrogen gas, carbonates make carbon dioxide. All of them will leave a neutral chemical after the reaction has finished, if all the acid has been used up.

Titration is a technique used to calculate the concentrations or amounts of substances. In an acid base titration you may have an acid that you don’t know the concentration of, and a base whose concentration you do know.

The technique is to measure out accurately a volume of the alkali of unknown concentration into a flask, and fill up a burette with the acid. Add some indicator solution to the acid in the flask, so that when all the acid has reacted with the base, there will be a colour change. The burette is graduated. You then open the tap on the burette and let the acid run into the flask. Once all the acid has reacted with the base, you get a colour change and you turn off the tap. You can now read off the volume of base you’ve added.  From this you can workout the concentration of the acid.

As I know all the concentrations of the acids and alkalis given I can do another experiment, which is to measure the heat of neutralisation otherwise known as the enthalpy of neutralisation.

Enthalpy is the measure of energy usually heat energy that a substance has. You can’t measure enthalpy directly, but you can measure the change in enthalpy when a reaction happens. There is a change in enthalpy when an acid neutralises an alkali. The reaction flask gets warm because an exothermic reaction happening. Heat is given off because new O-H bond H2O has been formed. An exothermic reaction is one where heat energy is being lost to the surroundings. The enthalpy of the salt solution made when an acid and alkali mix together has gone down. It has lost energy as heat to the surroundings.

Different acids and alkalis will make a difference to the enthalpy. The reason why enthalpy happens is because in order to make new substances you have to break existing bonds and then make new bonds between all the atoms in the mixture. This requires energy. Different acids and alkalis will need different amounts of energy to start the reaction, and will give out different amounts of energy when the have finished reacting.

The unit of enthalpy is kJ per mole (kJ/mol). 


  1. Burette
  2. Metal stand to hold burette
  3. Conical flask
  4. Alkali solution
  5. Acid solution
  6. Data logger
  7. Thermo probe
  8. Stirring rod
  9. Pipette
  10. Universal indicator Solution (U.I.S)
  11. Polystyrene cup


For the first experiment I will pipette 25cm3 of sodium hydroxide of 2 moles/dm3 into the polystyrene cup. I will measure the temperature of the sodium hydroxide in the polystyrene cup. I will then from the burette run in 5cm3 of hydrochloric acid whilst stirring the solution with a stirring rod. I have to know the exact amount added each time and measure the temperature. I will continue doing this, adding 5cm3 of acid and measuring the temperature until the burette is empty.

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I will then repeat this experiment but using the same solutions at different concentrations.

I will make this experiment safe as both the acid and the base solutions are corrosive and should be handled with care. I will wash off any acid or base that gets on my skin or clothing. When I will use a pipette I shall use a rubber bung. I will not stir the solution with the thermo probe; so I will use a separate stirrer. I will also wear safety goggles.


When I mix the acid with the alkali, a neutralisation reaction takes ...

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***** This account is detailed throughout. There is relevant background theory, full explanations for steps followed and carefully worked calculations.