Chemistry: Investigating the Effects of Concentration on a Titration Curve

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Investigating One Factor That Affects How The pH Changes During a Titration Introduction: In this experiment I will be investigating how a certain factor changes the pH during a titration. pH changes when acid is added to alkali, or vice versa, as the ions in each are able to neutralise each other. The H+ ions, found in all acids, bond with the OH- ions, found in all alkalis, to form the completely neutral molecule water, or H2O, as shown by this symbol equation: H+(aq) + OH- (aq) ( H2O (l) The pH of a solution of acid would start at 1 or two, and be deep red in colour when tested with universal indicator, but when alkali begins to be added, therefore starting to neutralise some of the H+ ions, the pH will start to increase. When there is a complete balance between the amount of H+ in the acid and OH- in the alkali, this would mean the solution is completely neutral, and at this point it would have a pH of 7, and would be green in colour through testing with universal indicator. Once more alkali is added to this, the solution will begin to increase again in pH, going up to 12 – 14, and being blue/purple in colour through testing with indicator. This would be because there would then be more OH- ions. Hypothesis and prediction: Concentration of an acid affects the pH during a titration. As the concentration of the acid increases, I predict that the volume of alkali needed to change the pH to reach an end point will also increase. I also predict that doubling the concentration of acid will require double the amount of alkali to reach an end point. This would be due to there being more hydrogen ions present in a more concentrated acid, and therefore more OH- ions needed to neutralise these. When concentration doubles, this means there is twice as many H+ ions; therefore twice as much alkali will be needed to balance them out. Apparatus list:

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