Lab

1. Chlorophyll Lab<br />IB Biology SL, Period 7<br />Billy Egnehall, Grade 11<br />PigmentColorRf valueCaroteneYellow0.95XanthophyllYellow-Brown0.71Chlorophyll aBlue green0.65Chlorophyll bOlive green0.45<br />Table 1: This table shows the different Rf values for the solvent of 90% acetone, and 10% petroleum ether<br />Data Collection:<br />PigmentColourObserved Rf ValueOriginal Rf ValuePercentage Error±1Chlorophyll BOlive Green0.310.4531%Chlorophyll ABlue Green0.430.6534%XanthophyllYellow Brown0.580.7118%CaroteneYellow0.730.9523%<br />Table 2: This table shows observed data collected of Rf values compared to the original/correct Rf values of the same pigments <br />Calculations:<br />Total length of paper slip = 175 mm±1<br />Length of Chlorophyll B = 54 mm±1<br />Length of Chlorophyll A = 76 mm±1<br />Length of Xanthophyll = 102 mm±1<br />Length of Carotene = 128mm±1<br />Observed Rf Value = (length of observed pigment colour/ total length of paper slip)<br />Percentage Error = {(original Rf value – observed Rf value)/original Rf value} x 100%<br />Chlorophyll B:<br />54/175=0.31{(0.45-0.31)/0.45}x100=31%<br />Chlorophyll A:<br />76/175=0.43{(0.65-0.43)/0.65}x100=34%<br />Xanthophyll:<br />102/175=0.58{(0.71-0.58)/0.71}x100=18%<br />Carotene:<br />128/175=0.73{(0.95-0.73)/0.95}x100=23%<br />Conclusion:<br />When the observed Rf value was compared to the expected Rf value as seen in table 2, it shows that there was quite a phenomenal percentage difference. There were percentage differences ranged from 18% to 34%. Also as the Rf value grew higher, the lower the percentage of difference the observed Rf value was to the expected Rf value. Even with an uncertainty of ±1 mm the difference of the compared Rf values would remain significantly different because there are many factors which is involved in the process of the experimentation and only a few of which can be controlled. <br />Evaluation:<br />Though out the experimentation some limitations might have occurred and there are many improvements which could have been done to prevent them. Some limitations in experiment would be the dividing lines of the different pigment colours. Some of them were thick which made a clear measurement of the Rf value difficult and hard to keep constant. Another limitation in this experiment would be that of the amount of chlorophyll that is scraped onto the paper. As only a coin was used to scrap off the chlorophyll a number of time, there is no specific measuring tool that can be used to measure the exact amount of chlorophyll that was put on the paper. <br />Some improvements which would be applied for further experimentation of this experiment that would decrease the percentage differences between the observed Rf values to the expected Rf values would be that of the measurements used to measure the amount of chlorophyll that is scraped onto the piece of paper of which the experiment will be performed on.<br />