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Investigate the effect of changing the concentration of sodium hydroxide (alkali) on the volume of hydrochloric acid needed to neutralize a fixed volume of alkali by measuring the temperature and noting colour changes of the solution mixture.

Extracts from this document...

Introduction

College: Brookhouse six form Student: Miss Vincia Phillip Teacher: Mrs Zainab Topic: Titration/ neutralisation reactions Title: Titration/ Neutralisation Aim: To investigate the effect of changing the concentration of sodium hydroxide (alkali) on the volume of hydrochloric acid needed to neutralize a fixed volume of alkali by measuring the temperature and noting colour changes of the solution mixture. Background knowledge: Neutralization occurs when an acid is made to react with a base. In this reaction, the chemical opposites cancel each other out. Alkalis contain OH? (aq) ions, whereas acids contain H? (aq) ions. In the neutralization reaction the OH? and H? ions come together to form water; (H O), which is a neutral substance. The reaction to be carried out will be between Sodium hydroxide (NaOh) and Hydrochloric acid (HCl). Equations: Sodium hydroxide +hydrochloric acid�Sodiumchloride+ Water NaOh (aq) +HCl (aq) �NaCl (aq) +H O (aq) Equation: H? (aq) + OH? (aq) �H O (l) In this reaction there are four different ions. These are Na, OH?, H and Cl?. The reactivity series shows elements in order of their reactivity. Reactivity is based on how vigorously elements react with oxygen, air and dilute acid. In displacement reactions, more reactive elements displace others from their compounds and take their place. Spectator ions are ions which are indirectly involved in the reaction. In neutralization reactions the spectator ions are usually the most reactive. The spectator ions in this reaction are Na and Cl?. Na and Cl? come together to form NaCl (aq), (sodium chloride). Because sodium is more reactive than hydrogen in this reaction, it displaces hydrogen form hydrochloric acid and takes its place. Before Reaction After Reaction The pH scale is used to measure the acidity or alkalinity of an aqueous solution, across a 14 point scale. Substances with a pH of 1-6 are acidic in nature. Those with a pH of 8-14 are alkaline. PH 7 represents a neutral solution. ...read more.

Middle

The mixture was stirred briefly using the thermometer, and the temperature and colour recorded. 5. Step 4 was repeated until a total of 40cm� of dilute hydrochloric acid was added to the cup. 6. The procedure from steps 1-5 were repeated three times using three different concentrations of alkali;0.5,1 and2 moles, and 1molar concentration of the acid. 7. In the case of wide variations in the replicates, the experiments were repeated. 8. The results were then be plotted on a graph of neutralization as shown bellow: Safety: In this experiment the chemicals to be used are corrosive. Safety gears such as goggles and lab coats should therefore be used to protect the eyes and skin. Also the area where the experiment is to be carried out should be cleared so that unnecessary accidents will be prevented. Fair test: To ensure that my results are accurate and reliable, I shall do the following: A reliable three sets of readings will be taken. This will ensure that accurate temperature readings are obtained. The readings will also ensure that there are no anomalous readings. Ensure valid-control of all factors which can affect my results. TABLE SHOWING FACTORS THAT CAN AFFECT THE EXPERIMENT AND THE WAYS IN WHICH THEY WILL BE CONTROLLED. Factors that can affect the experiment Effect on experiment How it will be controlled Volume of acid Acids contain hydrogen ions which is the chemical opposite of an alkali. Measure the acid carefully using the most appropriate apparatus. In this case a burette will be used because the acid will be gradually added to the alkali 2ml at a time till a total of 40 ml is added. Volume of alkali Alkalis contain hydroxide ions which is the chemical opposite of an acid. Measure the alkali solution carefully, using the most appropriate apparatus. In this case a measuring cylinder will be used. This appropriate because a fixed volume of alkali will be used. ...read more.

Conclusion

A burette was used to deliver the second reactant to the flask and universal indicator was used to detect the endpoint of the reaction. This method, used to investigate the 'effect of changing the concentration of an alkali on the volume of acid needed to neutralise a fixed volume of alkali' is very effective method as the results obtained were approximately accurate. The results were not precise but approximate results. To improve the accuracy of the results obtained I would have made some changes to the apparatus used. A measuring cylinder was used to measure the volume of alkali added to the mixture. Measuring cylinders are used for mixing, transporting, and reacting, but not for accurate measurements. The volumes stamped on the sides are approximate and accurate to within about 5%. In the place of the measuring cylinder it would have been more appropriate to use a pipette. Pipettes are used to measure small amounts of solution very accurately. Pipettes come in a variety of sizes and are made to rigorous specifications. They are designed to deliver the stated volume, at the temperature specified, when used in the correct manner. The temperature of the room in which the experiment was carried out was not at normal room temperature. The room utilised was air-conditioned therefore temperature was lower than usual. The results obtained were reliable. However, if the experiment was to be repeated using the pipette and at normal room temperature, I believe that the results would not be the same. They would be more accurate than those previously obtained. There were no anomalous results. The temperature readings were in close proximity of each other therefore there was no problem in drawing lines of best fit on the graphs. Three sets of readings were taken for each part of the experiment. The results obtained all corresponded with the general pattern in the experiment. Therefore, they were good enough to draw firm conclusions. 1 ...read more.

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Here's what a teacher thought of this essay

4 star(s)

This is a very good investigation write up, looking at neutralisation and the factors that have an effect on it. There is no graph included within the write up, so I am unable to comment on its accuracy and analysis. 4 Stars

Marked by teacher Louise Star 21/06/2013

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