2019 Year 12 IB Extended Essays

H YPOTHESIS If the mass of cobalt (II) chloride increases, then the spacing between each precipitate Liesegang rings will also remain the same. This is based on the spacing laws of Jablczinsky and Mathur which use Ostwald’s model of supersaturation to show that the ratio of the distance between bands is equal.

V ARIABLES I NDEPENDENT

Mass of cobalt (II) chloride within gel solution. Measured using electrotonic balance with an accuracy of ± 0.0001 grams (g). Variations of 2.5000g, 3.0000g, 3.5000g, 4.0000g, 4.5000g have been used. D EPENDENT The distance in centimetres (mm) of n th ring to the gel surface. Specifically, the distance of each precipitate ring from the gel surface. This is measured using a 30cm ruler with an accuracy of ± 1 mm. C ONTROLLED The background research shows that there are many factors that affect the ring formation process. Factors such as illumination, temperature, and foreign compounds might affect the formation of precipitates. As a result of having a considerable number of factors affecting the formation of said rings, steps were taken to control and minimize as many of these factors: - The experiment was conducted with the same equipment to minimize any error. Each test tube and beaker were cleaned with deionized water to reduce the chance of any foreign compounds. Overall using the same equipment reduces the possibility of random error between trials. - To keep temperature as constant as possible I conducted the experiment at room temperature. Temperature for each trail was kept constant as each test-tube was stored

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