Bukunmis 2nd lab PDF

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NAME: AREELU OLUWABUKUNMI OLUWAMAYOWA STUDENT NUMBER: 7814893 LABORATORY DAY: TUESDAY LABORATORY SESSION: AM LABORATORY ROOM NUMBER: 206 ROTATION: 1 LOCKER NUMBER: 1229 EXPERIMENT NUMBER: 4 EXPERIMENT TITLE: SPECTROSCOPY ANALYSIS OF SPINACH DATE AND TIME OF EXPERIMENT: 14TH OF MARCH,2017. AM DATE AND TIME OF SUBMISSION: 16TH OF MARCH,2017. PM

PURPOSE The purpose of the experiment was to use a spectrometer to identify compounds present in spinach, and to determine the iron content of spinach. ANALYSIS Graph wavelength vs absorbance: Spectrum of the spinach extract 3

absorbance

2.5 2 1.5 1 0.5 0 375

425

475

525

575

625

675

725

wavelength(nm)

Final concentration of iron(III) in the five 10mL test tubes Test tube 1: The working formula is C1 V 1=C 2 V 2 V 2=Total volume∈the test tube. V 1=volume of FeCl3 added C1 =concentration of FeCl 3 added C 2 =concentration of FeCl 3∈the test tube

C2

=

(0.00025 M )(1.0∗10−3 L) (1 0∗10−3 L)

= 0.000025M

Test tube 2: C2 = 0.00005M Test tube 3: C2 = 0.000075M Test tube 4: C2 = 0.0001M Test tube 5: C2 = 0.000125M Concentration of iron(III) (M) Absorbance (A)

0.000025 0.00005 0.000075 0.0001 0.000125

0.205 0.374 0.548 0.841 1.045

Graph of iron(III) concentration vs absorbance : iron(III) concentration vs absorbance

Absorbance (A)

1.2 1

f(x) = 8588 x − 0.04 R² = 0.99

0.8 0.6 0.4 0.2 0

0

0

0

0

0

0

0

0

concentration of iron(III)(M)

CALCULATION CONCENTRATION OF IRON(III) IN SPINACH EXTRACT Obtained from graph Y= absorbance =0.734 Y= 8588x- 0.0415 0.734 = 8588x- 0.0415 X= 0.0000903M Concentration = 0.0000903m/L n= CV n= 0.0000903m/L X 0.02L n= 0.00000181 mol

molar mass of Fe = 55.85 g/mol mass of Fe in spinach = 55.85 g/mol X 000000181 mol Mass of Fe in spinach = 0.000101g Per 100g of spinach: = 100g X 0.000101g =0.0101g =10.1mg DISCUSSION From the graph, it appears that the spinach extract has the highest absorbance at 439 nm which falls within the range of purple light. The wavelength of purple light of purple light is at 400nm. This implies that purple light is absorbed by the spinach extract since there is a high absorbance at this wavelength. The graph is at its lowest at the 517nm range. This corresponds to the wavelength of green to yellow light. It also indicates that the spinach extract does not absorb the green and yellow light very well. The graph reaches another peak around the 667nm range but is not as high as the absorbance of the purple light. 667nm also falls within the range of red-orange light. The graphed data from the spectrometer corresponds to the graph of chlorophyll a because they have their peak at the same range. This indicates that the chlorophyll a compound is likely present within the spinach extract. The presence of the chlorophyll a compound is what gives the spinach its green colour. When the UV-light pen was shone on the spinach extract in the cuvette , a red colour was observed within the medium but became blue again at the opposite side of the cuvette. The original colour of the UV light was blue. The red hue that appeared was due to the emission of photons. When exposed to light, the electrons become excited and then reach higher energy levels. The relaxation of the electrons and the

subsequent drop back to the ground state caused them to emit some of the energy as light. The red light was observed when the laser light was shown on the cuvette was because of the second peak where the spinach had the second highest absorbency value which caused this wavelength of light to be emitted. My values for the amount of iron in mg per 100g of spinach did not match the recorded value for the amount of iron in mg per 100g of spinach which was 2.71mg. I do not expect all spinach to contain the exact same amount of iron because the recorded value must have been the average of the amount of iron found in 100g of spinach. Also the spinach would have been grown in different soils, some richer in iron and some deficient in iron content. Also environmental conditions may have affected the content of iron in the spinach. The amount of liquid extracted from the filtered solution was less than the required 5mL. This increased the concentration of the solution. CONCLUSION I concluded that the compound chlorophyll a was present within the spinach based on the data and the information given in the lab manual. I am 40% certain of the values I got for the amount of iron present in 100g of spinach as it does not match the value from the recorded. However I am 90% certain that the spinach contains the compound chlorophyll a....