CHM256 LAB Report EXP 12 PDF

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CAWANGAN TERENGGANU KAMPUS BUKIT BESI FACULTY OF APPLIED SCIENCE

CHM256 BASIC ANALYTICAL CHEMISTRY LABORATORY REPORT GRAVIMETRY II : GRAVIMETRIC ANALYSIS OF PHOSPHORUS IN PLANT FOOD

NAME : NUR AYUNI BINTI JOHARI STUDENT ID : 2020464586 GROUP : AS121 2B6 GROUP MEMBERS : NO 1 2

NAME NUR NABILAH BINTI ZULKIFLI NUR HANI AINA BINTI MOHAMED HARIS

STUDENT ID 2020475328 2020892046

NO OF EXPERIMENT : 12 DATE OF EXPERIMENT : 4TH MAY 2021 DATE OF SUBMISSION : 24TH JUNE 2021 LECTURER : MADAM SITI MUNIRAH MUDA

INTRODUCTION The basis of gravimetric analysis is mass measurement. Gravimetric analysis entails isolating an ion in solution by a precipitation process, filtering, washing the precipitate free of impurities, converting the precipitate to a product of known composition, and lastly weighing and calculating the precipitate's mass by difference. The quantity of the initial ion may be calculated using the mass and known composition of the precipitate. Many of the procedures for gravimetric analysis of silver and chlorine were invented or specified by Theodore W. Richards (1868-1928) and his Harvard graduate students. These approaches were utilized to estimate the atomic weights of 25 elements, decompose known compound weights, and apply gravimetric methods to measure the chloride concentration.

OBJECTIVES To determine the content % of P in plant food through gravimetric analysis.

APPARATUS 1. Weighing boat / bottle / paper 2. 250 mL beaker 3. Filter funnel 4. Dropper 5. Measuring cylinder 6. 100 mL and 250 mL volumetric flask 7. Retort stand, white tile, hotplate 8. Porcelain evaporating dish

CHEMICALS 1. MgSO4 . 7H2O (10%) 2. NH3 (aq) 2 M (100 mL) 3. 75% isopropyl alcohol

PROCEDURE Firstly, we obtained our plant food sample and recorded the set of numbers written on the label. The plant food sample between 3.0 – 3.5 g was weighed using a weighing paper and the sample transferred to a 250 mL beaker. Then, 35 – 40 mL of distilled water added and the mixture was stirred with a glass rod to dissolve the sample. The insoluble material was removed through filtration if the sample did not completely dissolve. To filtrate, 40 mL of 10% MgSO4 . 7H2O was added. Then, about 100 mL of 2 M NH3 (aq) was added slowly while stirring. A white precipitate of MgNH4PO4 . 6H2O will form. After that, the mixture was allowed to sit at room temperature for 10 minutes to complete the precipitation. We weighed accurately a filter paper. The paper was folded and fit it into a glass funnel. We wetted the paper with distilled water to hold it in place in the funnel. The precipitate and all the solution transferred carefully from the beaker onto the filter paper. Next, the precipitate washed by adding 2-3 times of 5 mL portions of distilled water to the beaker. Then, the precipitate rinsed again with two 10 mL portions of 75% isopropyl alcohol through the filter paper. After that, the filter paper was removed and placed on a numbered porcelain evaporating dish and stored to dry for 2-3 days on the bench or in the oven for 24 hours at 60oC. Lastly, when the MgNH4PO4 . 6H2O was thoroughly dry, the filter paper plus the MgNH4PO4 . 6H2O were weighed. The mass recorded and the % of phosphorus in the original sample calculated.

RESULTS / DATA Plant food name : Miracle Grow All Purpose Plant Food % of Phosphorus content written on the label : 8% Mass of sample used : 3.4324 g Mass of filter paper + MgNH4PO4

0.8789 g

Mass of filter paper

0.3793 g

Mass of MgNH4PO4

0.4996 g

QUESTIONS a) Use gravimetric factor and mass of MgNH4PO4 to calculate : i.

The mole of P

ii.

The mole of P2O5

b) The phosphorus content in plant food is usually expressed in term of P2O5. Calculate the mass and content % (w/w) of P2O5 in the sample.

c) Compare your result from the amount (w/w %) stated on the label of the plant food. Calculate the % error.

DISCUSSION It was established that the fertilizer sample had a percent P of 8% and a percent P 2O5 of 7.539 % based on the results. It shows that percent error between both of these percent is 5.76%. The chemical equation involved in this experiment is 2NH4+ (aq) + 2HPO42+ (aq) + Mg2+ (aq) + 4H2O (l) + 2OH- (aq)  2MgNH4PO4 . 6H2O (s). It should be emphasized that NH3 is gently added to the solution with constant stirring to guarantee precipitate development, resulting in a precipitate that is simpler to filter and devoid of contaminants. The von Weirman's ratio, which states that the particle size of a precipitate is inversely proportional to the value of Relative Superaturation, is related to this method. Some precaution steps that could be taken is to assure the appropriate production of crystals required by the experiment, a specified method of adding the precipitating agent, such as dropwise addition or specific quantities per second, or stirring, would be used. It should also be noted that when the combination is digested or left to remain without agitation, it should be covered to avoid contaminants in the air.

CONCLUSION In conclusion, the typical phosphate fertilizers, on the other hand, include at least 42.5 % water soluble phosphates and 46 % total phosphates by weight. Depending on the type of fertilizer used in the experiment, the theoretical values will differ.

REFERENCES 1. Gravimetric Determination of Phosphorus in Plant Food.. (2005, November 30). In WriteWork.com, June 19, 2021. https://www.writework.com/essay/gravimetric-determination-phosphorus-plant-food

2. Gravimetric Determination of Phosphorus in Fertilizer Samples. (2017, Jan 04). http://studymoose.com/gravimetric-determination-of-phosphorus-in-fertilizersamples-essay

3. StudyMoose. (2021, February 23). Gravimetric Determination of Phosphorus in Fertilizer Samples Free Essay Example. https://studymoose.com/gravimetricdetermination-of-phosphorus-in-fertilizer-samples-essay...