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Questions and Answers
What does Analytical Chemistry determine?
The chemical composition of samples.
Which of the following is NOT an application of Analytical Chemistry?
What is a sample in the context of Analytical Chemistry?
A subset of a population taken for analysis.
A gross sample is the individual samples collected.
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Dissolved lead and total lead concentration can yield the same results.
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What is the difference between homogeneous and heterogeneous samples?
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The concentration of total metal in a water sample is determined by ________ the sample.
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What is the goal when taking samples in Analytical Chemistry?
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Which factors may affect the concentration of lead in lake water?
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What is Analytical Chemistry?
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What are the two main types of analysis in Analytical Chemistry?
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Which of the following is a use of Analytical Chemistry?
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What does a sample represent in Analytical Chemistry?
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What is a gross sample?
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The concentration of lead in Lake Ontario water is expected to be the same everywhere in the lake.
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What is the difference between dissolved and total metal in a water sample?
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How do you determine the concentration of dissolved metal in a water sample?
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What does it mean for a sample to be homogeneous?
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It's easier to get a representative sample from a heterogeneous population than from a homogeneous one.
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What is an analytical method?
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Study Notes
Analytical Chemistry
- The science and technology used to determine the chemical composition of samples.
- Answers the questions:
- What is in the sample? (qualitative analysis)
- How much of it is there in the sample? (quantitative analysis)
Uses of Analytical Chemistry
- Clinical: Tests on blood and other bodily fluids.
- Forensic: CSI.
- Environmental: Samples of rocks, soil, sediment, water, air, biota (plant and animal matter).
- Food: Determines what is in the food and how much.
- Quality control: Checks manufacturing processes (refineries, pharmaceuticals).
- Scientific research: Geology, anthropology, exploration of planets.
Samples
- A representative sample is taken from a population to infer information about the whole population.
- A sample is a subset of a population.
- Samples can be collected in bottles and called sampling units or sampling increments.
- The collection of samples is called the gross sample.
Representative Samples
- The goal is to collect a sample that reflects the composition of the population at the time of sampling.
- The meaning of analytical results can be specific, and may not be as straightforward as first thought.
- For example: "What is the concentration of lead in Lake Ontario water?"
Dissolved vs. Total Metals
- Environmental water samples may contain solid particles (solid, silt, sand, sediment, algae).
- Metals can be dissolved in water or attached to solid particles.
- Total metal includes both dissolved and undissolved metal.
- To find the concentration of dissolved metal, filter the water to remove undissolved particles.
- To find the concentration of total metal, digest the water sample (to dissolve all the metal) and measure the metal concentration in the digestate.
Homogeneous and Heterogeneous Samples
- Samples can be homogeneous or heterogeneous.
- Homogeneous samples have a uniform composition throughout (e.g., a liquid solution without undissolved particles).
- Heterogeneous samples have distinct parts that can be easily observed (e.g., soil samples).
Achieving Homogeneity
- It's easier to obtain a representative sample from a homogeneous population (e.g., water).
- It's harder to obtain a representative sample from a heterogeneous population (e.g., soil).
Analytical Methods:
- Documents that describe the process of chemical analysis.
Analytical Chemistry
- The study of how to determine the chemical composition of samples.
- Analyzes both qualitative and quantitative aspects of a sample.
- Qualitative analysis answers: "What is in the sample?"
- Quantitative analysis answers: "How much of it is there in the sample?"
Application of Analytical Chemistry
- Clinical: Analyzing blood and bodily fluids.
- Forensic: Criminal investigations.
- Environmental: Analyzing samples of rocks, soil, sediment, water, air, and biota (plants and animals).
- Food: Determining the composition and quantity of components in food.
- Quality Control: Monitoring manufacturing processes in industries like refineries and pharmaceuticals.
- Scientific Research: Supporting various fields like geology, anthropology, and planetary exploration.
Understanding Samples
- A population refers to the entirety of the substance being analyzed.
- Samples are subsets taken from the population to represent its properties.
- Sampling units or increments are individual portions collected.
- A gross sample is the collection of individual samples.
Representative Samples
- The aim of sampling is to obtain a representative sample that accurately reflects the population's characteristics.
- Homogeneous samples have consistent composition throughout (e.g., liquid solutions without undissolved particles).
- Heterogeneous samples have visually distinct components (e.g., soil samples).
Specificity in Samples
- Understanding the meaning of analytical results requires defining specific parameters.
- Location: Would lead concentration vary within a lake at different depths or areas?
- Time: Could measurements differ depending on the day, time of day, or season?
- Dissolved vs. Total: Distinguishing between dissolved metals and metals attached to suspended particles is critical.
Dissolved vs. Total Metals in Water
- Water samples often contain undissolved particles like silt, sand, sediment, and algae.
- Total metal includes both dissolved and undissolved metal attached to particles.
- To determine dissolved metal, filter the water to remove undissolved particles before measurement.
- To determine total metal, digest the sample (typically by boiling in acid) to dissolve all metal before measurement.
Analytical Methods
- Once samples reach the laboratory, they are analyzed using analytical methods.
- Analytical methods are written documents clearly outlining the procedures, equipment, and data interpretation involved in the analysis.
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Description
This quiz delves into the field of analytical chemistry, exploring its methods for determining the chemical composition of various samples. It covers qualitative and quantitative analysis, applications in clinical, forensic, environmental, and food sciences, as well as the importance of representative sampling in obtaining accurate results.
