2019 Year 12 IB Extended Essays

D ATA A NALYSIS As seen in graph 1 there is a positive relationship in all variations between the ring number and its distance from the gel surface. This shows that the higher the ring number the further it is from the gel surface. The graph also shows that the mass of cobalt (II) chloride is not proportional to the rings distance. This is seen by the fact that the rings created by 2.5 grams of cobalt chloride are each further away from the gel surface than any other variation. With the 5 th ring being 33 mm further away from the gel surface than it was with 4.0 grams. It is actually a decreasing trend. The more cobalt (II) chloride within the solution the earlier the rings are formed. This is trend can be explained with Ostwald’s model of supersaturation, the precipitate that creates the ring formations only occurs once the saturation value overcomes its critical value. With less cobalt (II) chloride in the solution the ammonia has to diffuse for a longer period before this critical value is reached. Therefore, the first ring will be further from the gel surface. The data collected supports both Ostwald’s model of supersaturation as well as the spacing laws explained in the background research. The spacing law states that the ratio between a band and its adjacent band is constant. Even though the mass of cobalt (II) chloride was changed and ring formation is quantitatively different the spacing coefficient of each variation is 1, as seen in table 5. Enforcing the notion that the spacing laws can be applied to any Liesegang structure. The spacing law is also visually show in the graph. Below is a table showing the equation of each trend line:

T ABLE 6: TABLE SHOWING TREND LINE EQUATIONS Mass of Cobalt (II) Chloride in grams

Equation of line = 1.1x + 38.9 = 1.2x + 24.6 = 1.1x + 17.4 = 1.3x + 16.1 = 1.1x + 5.99

2.5 3.0 3.5 4.0 4.5

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