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An Investigation of Titration

Extracts from this document...

Introduction

Introduction I am going to do an investigation on how much acid is needed to neutralise a certain amount of alkali. The acid that I will use is hydrochloric acid and the alkali I will use is sodium hydroxide. Hydrochloric Acid Hydrochloric acid (HCl) contains hydrogen and chlorine and is ionically bonded. Hydrochloric acid looks like this: Sodium Hydroxide Sodium Hydroxide (NaOH) is made up from Sodium, Hydrogen and oxygen. NaOH is ionically bonded and it looks like this: Acids, Alkalis and Neutralisation An acid is a proton donor and an alkali is a proton receiver. An Acid will have a pH less than 7 and an alkali will have a pH of more than 7. An acid with a pH of 1 is the strongest as ALL of the Hydrogen ions are ionised. The strongest alkali, with a pH of 14, is when ALL the hydroxide ions are ionised. Neutralisation is when an acid and an alkali of equal strengths are mixed, the pH will be 7 and salt and water is produced. In more detail it is when ionised hydroxide and hydrogen meet and share electrons. When a substance is diluted the concentration is weakened. The molarity changes when the water is added. The indicator will change colour when neutralisation occurs, also the temperature will stop rising. ...read more.

Middle

My next diagram will show how I read the liquids in measuring cylinders and burettes: Health and Safety * The sodium hydroxide is very soapy so do not get it on the outside of beakers and other equipment as it is easy to drop. * Place apparatus at a safe height so that people know its there and don't accidentally knock it over. * Use a conical flask when measuring the temperature with a thermometer as beakers will tip over. * Wear a white coat to protect yourself from spillage of acids or alkalis. * Put a piece of white paper underneath the beakers so that you know where you have spilt something and what you have spilt. * Make sure the clamp stand is tight enough to support the burette but not smash it. Exothermic and Endothermic Reactions Exothermic Reaction An exothermic reaction is when heat is given out during the reaction and heats up itself and the surroundings. Also in an Exothermic Reaction the products have less energy than the reactants. This graph shows an exothermic reaction, the neutralization reaction gave out heat as we added the acid to the alkali. We did a second set of experiments to measure the heat produced from the reaction and to see if heat was no longer produced after neutralization. ...read more.

Conclusion

Because temperature affects reaction rate, the reaction must affect the temperature, so when all of the molecules have formed another compound (NaCl + H2O in my investigation) the temperature must decrease because there are no more molecules able to break bonds. Evaluation If there was no human error I believe that the titration experiment would show that 20.00ml of acid is needed to neutralise 20.00ml of alkali. I could have done better in my experiment by spilling less, I should have began using a conical flask rather then a beaker and this would have stopped me from spilling the alkali. The spillages took time to clean up making me have to rush my experiment and therefore made me more likely to make mistakes. However I do believe that my results were overall consistent and accurate, the human error was minimal. For example my tables showed that after 20ml of acid was added; the temperature always decreased. There were not any anomalies in the results. Using an ammeter and a simple circuit I could investigate when neutralisation occurs by passing a current through it. This is a diagram of the experiment I could undertake: I will be able to tell exactly when neutralisation occurs because the Ammeter will show a sudden drop in current. This is because the H+ and OH- molecules ionically bond to form water which will weaken the electrolyte therefore weakening the current passing through it. ?? ?? ?? ?? Tom Burgess Yr 11 set 1 Chemistry Coursework ...read more.

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Response to the question

The essay is of a reasonable standard, with few factual errors, but the standard of English could be improved, there is no graph, and some over-generalisations have been made. Hydrochloric acid is covalently bonded, not ironically bonded. The author has ...

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Response to the question

The essay is of a reasonable standard, with few factual errors, but the standard of English could be improved, there is no graph, and some over-generalisations have been made. Hydrochloric acid is covalently bonded, not ironically bonded. The author has implied that all acid-alkali neutralisations have a 1:1 acid:alkali ratio when this is not always the case. The author does answer the question set “How much acid neutralises a certain amount of alkali?”, but probably should have made the question more specific because their experiment is only on a single acid and a single alkali.

Level of analysis

The author could have expanded their experiment to cover multiply acids and alkalis, and if I had conducted this experiment and had had the time, I would have done so. It is excellent that the author mentioned the bonding in the molecules, but needed to check their facts before submitting their coursework. It was good that they put in the equation “acid + alkali --> salt + water” and putting in “HCl + NaOH --> NaCl + H2O” was also useful. Their explanation of the pH scale was slightly inaccurate, but that may be simply because they are doing GCSE chemistry. Their neutralisation shows reasonable results, but they did not give the concentrations of the acid or alkali, which they should have done. Ideally the author would have considered some of the major problems before doing their experiment (such as spilling things) and tried to eliminate them before conducting it. They could have improved their experiment by doing more neutralisations, and then creating a graph with error bars. They could also have used different amounts of acid and alkali to check the trend continued. The same applies to the investigation into temperature.

Quality of writing

The author uses scientific vocabulary to good effect, but makes some grammar errors, and could make their writing more sophisticated. I think had they expressed themselves better their coursework could have been improved.


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