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Describe a laboratory or field method to show any two of the following: (a) The presence of a named mineral nutrient in a soil sample - Leaving Cert Agricultural Science - Question 4 - 2006
Question 4
Describe a laboratory or field method to show any two of the following: (a) The presence of a named mineral nutrient in a soil sample. (b) The extraction of pigmen... show full transcript
Worked Solution & Example Answer:Describe a laboratory or field method to show any two of the following: (a) The presence of a named mineral nutrient in a soil sample - Leaving Cert Agricultural Science - Question 4 - 2006
Step 1
(a) The presence of a named mineral nutrient in a soil sample.
Answer
To test for the presence of a named mineral nutrient such as nitrate in a soil sample, follow these steps:
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Collect the Soil Sample: Use a soil auger to collect a soil sample from the field, ensuring it is representative of the area.
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Prepare the Apparatus: Gather the necessary equipment which includes a beaker, filter paper, funnel, and test tubes.
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Add Distilled Water: Place the soil sample into a beaker and add distilled water to create a soil suspension.
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Shake and Filter: Shake the mixture thoroughly to ensure the nutrients are dissolved, then filter out the solid particles using filter paper and a funnel.
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Add Reagents: To the filtered solution, add a reagent such as ammonium molybdate, followed by dilute nitric acid. This will react with the nitrate present.
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Observe Color Change: A color change in the solution indicates the presence of nitrate. Use a color chart to determine the concentration.
Step 2
(b) The extraction of pigments from a sample of grass.
Answer
To extract pigments from a sample of grass, you can perform the following steps:
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Prepare the Grass Sample: Grind fresh grass leaves using a mortar and pestle to break down the cellular structure. This increases the efficiency of pigment extraction.
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Dissolving the Pigments: Add a solvent such as alcohol (ethanol) to the ground grass to extract the pigments. Mix thoroughly and allow it to stand for a few minutes.
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Filter the Mixture: Filter the mixture through filter paper to separate the liquid containing the pigments from the solid grass residue.
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Chromatography: Place a drop of the filtrate on chromatography paper, and run a chromatography experiment by placing the paper in a jar containing a solvent mixture (e.g., acetone and petroleum ether).
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Analyze the Results: After the chromatography process, remove the paper and observe the separation of pigments along the paper. Identify the pigments based on their positions and colors. For example, chlorophyll can be one of the identified pigments.