1 Writ the procedure for the sampling of soil samples.
2 Define determinate errors. How we can reduce them.
3 What is significance of FF-test? Explain using a suitable example.
4 Briefly explain the extractions with diphenylthiocarbazone. How is change in pH useful in such extractions?
5 Discuss the extraction of an organic compound when it is present in the aqueous phase along with the impurities.
6 How is extraction of metal chlorides and nitrates carried out using solvation?
7 How can a mixture of three components be separated using ascending paper chromatography? Draw the suitable diagram and explain.
8 Give at least five examples each of mobile phases and locating agents used in paper chromatography
9 Briefly explain various factors affecting the efficiency of column chromatography
10 Why is selectivity coefficient of an ion exchanger important? Give the order of selectivity coefficients of different cations and anions.
Part B
11
Drive an expression for the ‘operational definition of pH .
12 Discuss design and working of calomel and glass electrodes.
13 Describe different factors effecting conductance.
14 A conductivity cell shows a resistance of 3950 Omega3950 \Omega at 250 C when filled with the experimental solution and 4864 Omega4864 \Omega at the same temperature when filled with 0.02 M KCl solution. If the conductivity of the solution is 2.767 xx10^(-3)Scm^(-1)2.767 \times 10^{-3} \mathrm{~S} \mathrm{~cm}^{-1}, calculate the conductivity of the experimental solution.
15 Describe the experimental setup of TGA. Taking suitable examples explain the effect of furnace atmosphere on TG curves.
16
An impure sample of CaC_(2)O_(4)*H_(2)O\mathrm{CaC}_2 \mathrm{O}_4 \cdot \mathrm{H}_2 \mathrm{O} is analyzed using TGA technique. TG curve of the sample indicates the total mass change from 85 mg to 30.7 mg when this sample was heated up to 1173 K . calculate the purity of the sample.
17
(a) Define electromagnetic radiation and state the relationship between the velocity and wavelength of an electromagnetic radiation.
(b) Molecular spectra are band spectra whereas atomic spectra are line spectra. Explain.
18
(a) State Beer and Lambert’s law and write its mathematical expression.
(b) What are monochromators? Explain the working of prism monochromator with the help of a suitable diagram.
19
(a) Calculate the number of vibrational degrees of freedom for ethane, C_(2)H_(6)\mathrm{C}_2 \mathrm{H}_6, explain the fingerprint and functional group regions in IR spectrum.
(b) Outline the advantages of premix burner in atomic spectroscopy. Discus structure of a laminar flow flame showing various zones.
20
List different excitation sources used for atomic emission spectrometry. Discuss the interferences observed in flame atomic emission Spectrometry
Answer:
Question:-1
Write the procedure for the sampling of soil samples.
Answer:
1. Introduction to Soil Sampling
Soil sampling is the process of collecting a portion of soil that is representative of a larger area for the purpose of analysis. This analysis can be used to assess soil fertility, composition, contamination, and other factors important for agriculture, environmental monitoring, or scientific research. Proper soil sampling ensures accurate and reliable results, which is critical for making informed decisions regarding soil management, crop production, and land use.
2. Importance of Soil Sampling
Soil sampling plays a crucial role in soil health assessment and management. In agriculture, it helps in determining the nutrient status of the soil, which is essential for effective fertilizer application. Environmental scientists use soil samples to evaluate contamination levels, such as heavy metals or pesticides, which may pose risks to ecosystems or human health. Soil sampling also aids in studying soil structure, texture, and microbial content, all of which impact soil quality and plant growth.
3. Types of Soil Samples
There are different types of soil samples, each serving a specific purpose:
Composite Samples: These are mixtures of soil samples taken from multiple locations within a sampling area. Composite sampling provides an overall representation of the soil conditions across a larger area and is commonly used for fertility testing.
Single Samples: These are soil samples collected from one location within a field or area. This type of sample is used when specific issues need to be addressed at a particular spot, such as high contamination or suspected nutrient deficiencies.
Layered Samples: These involve collecting soil samples from different soil horizons or layers, typically from the surface to a specified depth. Layered samples help assess the variation in soil properties at different depths, which is important for understanding soil profile dynamics.
4. Materials and Equipment for Soil Sampling
Before beginning the soil sampling process, it is essential to gather the necessary tools and materials:
Soil Probe or Auger: A tool used to extract soil from various depths in the soil profile.
Shovel or Trowel: Used to dig and collect soil from surface layers or when a soil probe is not available.
Plastic or Glass Containers: Clean containers are necessary for collecting and storing soil samples to avoid contamination.
Sieve: A tool to separate larger soil particles from smaller ones if necessary.
Labeling Materials: For labeling the soil samples with the date, location, and depth of collection.
Gloves: To maintain hygiene and avoid contamination from skin oils.
5. Procedure for Soil Sampling
The process of soil sampling involves several steps, each critical for obtaining accurate results.
Step 1: Determine Sampling Area
The first step in soil sampling is determining the boundaries of the sampling area. For agricultural purposes, this usually involves the entire field or specific zones within the field. For environmental assessments, the sampling area might be a specific site or location that is suspected to have contamination. It is essential to define this area clearly, as it will guide the sampling process.
Step 2: Choose the Sampling Method
Depending on the purpose of sampling, you will need to decide between composite, single, or layered sampling. For routine analysis like nutrient assessment, composite sampling is most commonly used. If you are looking at specific problems like contamination, single or targeted sampling may be necessary.
Step 3: Select Sampling Locations
For composite samples, choose multiple locations that are representative of the entire area. A general rule of thumb is to take samples from various spots in a zigzag or grid pattern, ensuring even coverage of the area. The number of sampling locations will depend on the size of the area; larger areas require more sample points. For a single sample, pick a location that reflects the specific issue you are investigating. In layered sampling, collect soil samples from different depths, such as the surface, 10 cm, 20 cm, and so on.
Step 4: Collect Soil Samples
Using a soil probe, auger, or shovel, collect a sample from the selected location. For composite samples, take samples from 6-10 spots within the area and combine them into one sample. Each sample should be taken from the same depth, typically the top 15-20 cm of soil for agricultural purposes. In the case of layered samples, extract soil at various depth intervals as specified.
Step 5: Prepare and Store Samples
Once the soil is collected, place it in clean containers. Avoid using metal containers if you are testing for trace metals, as metal can contaminate the sample. If the soil is wet, air-dry it in a clean, shaded area before sending it to the laboratory. Label each sample container with essential details such as the location, depth, date, and any other relevant information.
Step 6: Handle Samples with Care
Soil samples must be handled carefully to prevent contamination or changes in composition. Avoid touching the soil directly with your hands, especially if you are collecting samples for specific chemical analysis. Always wear gloves, and ensure that the tools and containers used for sampling are clean.
6. Analysis and Interpretation of Samples
Once the samples are collected, they are sent to a laboratory for analysis. Depending on the purpose of the sampling, various tests may be conducted, such as:
Nutrient Testing: To assess levels of essential nutrients like nitrogen, phosphorus, potassium, calcium, and magnesium.
Contamination Testing: To check for the presence of heavy metals, pesticides, or other pollutants.
pH Testing: To determine the acidity or alkalinity of the soil, which affects nutrient availability to plants.
Soil Texture and Composition: To assess the proportion of sand, silt, and clay.
The laboratory results will be used to make informed decisions about soil management, fertilization, irrigation, and environmental safety.
7. Conclusion
Soil sampling is a fundamental practice in agriculture, environmental science, and soil research. It provides valuable insights into soil composition, nutrient content, and contamination levels, which are essential for making informed decisions. By following a structured and methodical approach, one can ensure that the samples are representative and that the resulting data is accurate. Proper sampling techniques, appropriate tools, and meticulous handling of soil samples are crucial to the success of any soil analysis.
Question:-2
Define determinate errors. How can we reduce them?
Answer:
1. Introduction to Determinate Errors
Determinate errors, also known as systematic errors, are reproducible inaccuracies that consistently occur in measurements. These errors are usually predictable, and they arise due to inherent flaws in the experimental setup, the measuring instruments, or the methods used during the measurement process. Unlike random errors, which vary unpredictably, determinate errors have a consistent pattern, allowing them to be corrected once identified. Understanding the nature of determinate errors is crucial for improving the accuracy and precision of scientific experiments and ensuring reliable results.
2. Sources of Determinate Errors
Determinate errors can arise from various sources during an experiment or measurement process. These sources include:
Instrumental Errors: These errors are caused by faults or imperfections in the measuring instruments themselves. For example, a miscalibrated thermometer may give consistently higher readings. Over time, instruments like balance scales, thermometers, and spectrometers can drift from their original settings, causing repeated inaccuracies in measurements.
Observational Errors: These occur when the experimenter’s interpretation or reading of the measurement is flawed. For instance, parallax errors can occur if the observer does not read a scale or meter at eye level. Similarly, human error in recording data can lead to consistent inaccuracies in results.
Environmental Errors: These errors arise due to environmental factors such as temperature, humidity, or pressure. For example, chemical reactions might proceed differently at varying temperatures, or the density of a substance might change with changes in pressure or humidity, introducing a systematic error.
Methodological Errors: These errors are due to flaws in the experimental procedure itself. If a procedure is not followed correctly or uniformly, such as in titrations or calibrations, it can lead to a consistent error in the measurements.
Chemical Reactions: In analytical chemistry, determinate errors can arise from impurities in chemicals or solvents, which may alter the reaction yield or the concentration of substances being measured.
3. Characteristics of Determinate Errors
Unlike random errors, which are inherently unpredictable and occur by chance, determinate errors have the following key characteristics:
Predictability: Determinate errors occur consistently under the same conditions. Once identified, they can be anticipated and adjusted for, making them easier to correct.
Reproducibility: These errors produce similar results each time a measurement is taken, making them identifiable across repeated trials.
Correctability: Since determinate errors arise from identifiable causes (such as faulty equipment or incorrect measurement techniques), they can be corrected by calibrating instruments, adjusting methodologies, or using more precise instruments.
4. Methods to Reduce Determinate Errors
Reducing determinate errors requires understanding their sources and taking steps to mitigate them. Here are some practical strategies:
Calibration of Instruments: One of the most effective ways to reduce instrumental errors is to regularly calibrate measurement devices. Calibration ensures that the instruments provide accurate readings and are operating within the required specifications. For instance, using a standard reference material to calibrate a pH meter can minimize systematic errors in pH measurements.
Use of High-Precision Instruments: Employing more precise instruments can reduce the magnitude of determinate errors. For example, replacing a simple thermometer with a more accurate digital temperature probe can reduce temperature measurement errors.
Proper Training of Experimenters: Ensuring that the individuals conducting the experiment are properly trained can minimize observational errors. This includes training on correct reading techniques (e.g., how to read a burette without parallax) and how to handle instruments with care.
Environmental Control: To minimize environmental errors, experiments should be conducted under controlled conditions. For example, conducting reactions at a constant temperature and pressure can reduce errors related to environmental fluctuations. Proper storage and handling of reagents, especially those sensitive to light or temperature, also help reduce errors.
Use of Replicates: Taking multiple measurements or conducting replicate experiments can help identify and mitigate systematic errors. If the same error occurs in each replicate, it can be corrected by adjusting the experimental setup. Additionally, averaging the results of multiple trials helps to reduce the impact of any minor errors.
Elimination of Contamination: In chemical experiments, contamination of reagents or samples can introduce determinate errors. Ensuring that reagents are pure and that laboratory equipment is clean and free from contaminants will reduce such errors. For example, using high-quality, properly stored chemicals and cleaning glassware thoroughly before use can help avoid systematic errors in chemical analysis.
Optimization of Methodology: Refining experimental protocols and procedures can significantly reduce determinate errors. For instance, in a titration, ensuring that the endpoint is reached with precision (using an appropriate indicator or a pH meter) reduces potential errors in the final volume measurement.
5. Example of Determinate Errors and Reduction Strategies
Let’s consider a common example in volumetric analysis, such as a titration of a weak acid with a strong base. If the burette used is not calibrated correctly, the volume measurements of the titrant will consistently be off. This instrumental error can lead to a determinate error in the calculated concentration of the acid. To reduce this error, the burette should be calibrated before each use. Additionally, ensuring the endpoint is clearly defined by using a suitable indicator will help minimize observational errors.
Similarly, in environmental testing, if the air temperature is not controlled during the measurement of a substance’s concentration, it may affect the reaction rate, introducing systematic errors. This can be avoided by performing the experiment in a temperature-controlled environment or compensating for temperature fluctuations during data analysis.
6. Conclusion
Determinate errors are systematic, predictable, and reproducible inaccuracies that can be identified and corrected through proper experimental design, equipment calibration, and attention to environmental and procedural factors. While they cannot be eliminated entirely, their impact can be minimized by understanding their sources and employing corrective measures. By reducing determinate errors, we can increase the accuracy and reliability of scientific measurements, ensuring that experimental results are valid and consistent.