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The mass of lime added was 17.89 gm. With this amount of lime, the upflow velocity chosen was 10.71cm/min, because the lime remained suspended and it was assumed the apparatus would run for a longer time according to the results observed in Experiment 1.
Figure - 1 Apparatus for experiment 2, using a pH probe
The initial pH reading was 12 and stayed that way for 2 hours. It gradually decreased to 8.85 (saturation close to the pH of calcium carbonatea solution that is fully saturated calcium bicarbonate) by the 24th hour.
One of the possible explanations regarding the decrease of pH at a constant rate during the trial was that the upflow velocity was not enough to mix the lime and keep the dissolution. As a probe, it was increased to 16 cm/min. When this change was made, the probe registered an increase to a pH of 9.4.
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