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Analytical Chemistry > Chapter 8: Introduction to Analytical Chemistry > Flashcards

Chapter 8: Introduction to Analytical Chemistry Flashcards

1
Q

__ __ is the science of obtaining, processing, and communicating information about the composition and structure of __. In other words, it is the art and science of determining what __ is and how much of it exists. (American Chemical Society)

A
  • Analytical chemistry
  • matter
  • matter
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2
Q

a measurement science consisting of a set of powerful ideas and methods that are useful in all fields of science and engineering

A

analytical chemistry

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3
Q

Both __ and __ information are required in an analysis.

A
  • qualitative
  • quantitative
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4
Q

An analysis that reveals the identity of the elements and compounds in a sample.

A

Qualitative analysis

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5
Q

An analysis that indicates the amount of each substance in a sample.

A

Quantitative analysis

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6
Q

Give an example of a qualitative test done in the lab

A
  • Biuret test (protein test)
    –> diluting copper sulfate solution
    –> diluting hydroxide solution
    –> violet color (protein is present)
  • Iodine Test for Starch
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7
Q

How do ionic solids produce different colored flames?

A

Ionic solids can produce different colored flames due to the presence of metal ions in their composition. When these solids are heated or burned, the metal ions can become excited and emit light of a specific wavelength, which can result in a colored flame.

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8
Q

What is the principle behind the iodine test for starch?

A

Starch is a carbohydrate molecule found in food like bread. Its molecule is long and coiled, and the iodine ends up in the coil, which is why the iodine turns from light brown to purple and appears black at high concentrations.

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9
Q

How can the iodine test for starch be made quantitative?

A

By measuring the amount of light that passes through a sample containing the starch-iodine complex and interpreting or converting that measurement in terms of starch concentration, the method becomes quantitative.

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10
Q

Set up of quantitative analysis for Iodine Test for starch (7)

A
  • light source
  • collimator (lens)
  • monochromator (prism or grating)
  • wavelength selector (slit)
  • sample solution (in a cuvette)
  • detector (photocell)
  • digital display or meter
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11
Q

a chemical substance that is the subject of a chemical analysis.

A

analyte

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12
Q

What are the two measurements used in a typical quantitative analysis?

A
  1. Mass or volume of sample (gravimetric and volumetric methods)
  2. Measurement proportional to analyte amount (Electrochemical and spectrometric methods)
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13
Q

What methods are used for measuring the mass or volume of the sample?

A

Gravimetric and volumetric methods

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14
Q

What methods are used for measuring a quantity proportional to the amount of analyte?

A

Electrochemical and spectrometric methods

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15
Q

Classifications of quantitative analytical methods (4)

A
  1. Gravimetric methods
  2. Volumetric methods
  3. Electroanalytical methods
  4. Spectroscopic methods
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16
Q

A method used to determine the mass of the analyte or some compound chemically related to it.

A

Gravimetric method

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17
Q

A method based on the principle of precipitation or volatilization methods.

A

Gravimetric method

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18
Q

the analyte is converted into a solid precipitate through a chemical reaction. The precipitate is then filtered, washed, dried, and weighed. The increase in mass of the precipitate corresponds to the amount of analyte present in the sample. This method is based on the assumption that the precipitate formed is pure and stoichiometrically related to the analyte.

A

Precipitate method

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19
Q

This method involves converting the analyte into a volatile compound, which is then driven off from the sample by heating. The volatile compound is collected, typically in a suitable absorbent or trapping medium, and then weighed. The increase in mass of the absorbent or trapping medium corresponds to the amount of analyte present in the sample. This method relies on the assumption that the volatile compound formed is solely derived from the analyte and that no other volatile species interfere with the measurement.

A

Volatilization Method

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20
Q

A method used to determine the volume of a solution containing sufficient reagent to react completely with the analyte. It involves the measurement of the volume of a solution of known concentration, referred to as the titrant, required to react completely with a particular substance, or analyte, in the solution being analyzed.

A

Volumetric method

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21
Q

a solution of known concentration (the titrant) is slowly added to a solution of unknown concentration (the analyte) until the reaction between the two is complete. This is typically indicated by a change in color (in the case of an indicator) or a change in another measurable property (such as pH or conductivity).

A

volumetric titration

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22
Q

A method that involve the measurement of such electrical properties such as voltage, current, resistance, and quantity of electrical charge.

A

Electroanalytical method

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23
Q

A method based on measurement of the
interaction between electromagnetic radiation and analyte atoms or molecules or on the production of such radiation by analytes.

A

Spectroscopic method

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24
Q

How we see the color of an apple?

A

We see the color of an apple because of the way its pigments interact with light. The apple’s skin contains pigments like anthocyanin, which absorb certain wavelengths of light and reflect others. For example, red apples reflect red and orange wavelengths, making them appear red to our eyes.

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25
Q

General steps in a quantitative analysis (11)

A

> select method
acquire sample
process sample
> Is the sample soluble?
no: Carry out chemical dissolution
> measured property?
no: change chemical form
> Eliminate interferences
measure property x
calculate results
estimate reliability of results

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26
Q

What are some factors to consider when selecting an analysis method? (3)

A
  1. Level of required accuracy.
  2. Number of samples to be analyzed.
  3. Complexity of the sample and the number of components.
27
Q

What is involved in acquiring a sample for analysis? (4)

A
  1. Sampling - Obtaining a representative of the bulk. Sampling errors affect analysis reliability.
  2. Identifying heterogeneous materials.
  3. Conducting assays to quantify specific materials.
  4. Analyzing samples and identify substances.
28
Q

Acquiring the sample: A material is __ if its constituent parts can be distinguished visually or with the aid of a microscope.

A

heterogeneous

29
Q

acquiring the sample: the process of determining how much of a given sample is the material indicated by its name.

A

assay

30
Q

What happens during sample processing? (2)

A
  1. Sometimes, no processing is needed.
  2. Usually, the sample needs to be processed in different ways.
31
Q

Steps in processing the sample (3)

A
  1. Preparing a Laboratory Sample
  2. Defining replicate samples
  3. Preparing Solutions: Physical and Chemical Changes
32
Q

What steps are involved in preparing a laboratory sample for analysis for a solid sample? (4)

A
  1. Grinding solid samples.
  2. Mixing to ensure homogeneity.
  3. Storing before analysis.
  4. Drying solid samples.
33
Q

Why is grinding and mixing solid samples important?

A

To decrease particle size and ensure homogeneity.

34
Q

Why is it recommended to dry solid samples before analysis?

A

To prevent changes in chemical composition caused by water loss or gain.

35
Q

What should be done with liquid samples before analysis?

A

Evaporate solvent if necessary.

36
Q

portions of a material of approximately the same size that are carried through an analytical procedure at the same time and in the same way.

A

replicate samples or replicates

37
Q

improves the quality of the results and provides a measure of their reliability.

A

replication

38
Q

Quantitative measurements on replicates are usually averaged, and various __ __ are performed on the results to establish their reliability

A

statistical tests

39
Q

What is important when preparing solutions for analysis? (3)

A
  1. Complete dissolution of the sample by the solvent.
  2. Potential need for heating with various reagents.
  3. Possibility of ignition or high-temperature fusion.
40
Q

How should the solvent behave when preparing solutions for analysis?

A

It should rapidly and completely dissolve the entire sample, including the analyte.

41
Q

What reagents might be used during the preparation of solutions for analysis? (5)

A
  • Strong acids
  • strong bases
  • oxidizing agents
  • reducing agents
  • combinations thereof.
42
Q

Under what circumstances might the sample need to be heated during solution preparation?

A

when using strong acids, strong bases, oxidizing agents, reducing agents, or when performing high-temperature fusion.

43
Q

Few chemical or physical properties of importance in chemical analysis are unique to a single chemical species. Species other than the analyte that affect the final measurement are called __ or __.

A
  • interferences
  • interferents
44
Q

An interference is a species that causes an error in an analysis by __ or __ (__) the quantity being measured.

A
  • enhancing
  • attenuating (making smaller)
45
Q

Techniques or reactions that work for only one analyte are said to be __. Techniques or reactions that apply for only a few analytes are __.

A
  • specific
  • selective
46
Q

__ or __ is all of the components in the sample containing an analyte.

A

matrix or sample matrix

47
Q

Calibration and Measurement: Formula and explanation

A

c(sub)A=kX
the measurement of the property X is directly proportional to the concentration (cA).
where k is a proportionality constant.

48
Q

Computing analyte concentrations are based on the __ __ __ collected in the measurement step, the characteristics of the measurement instruments, and the stoichiometry of the analytical reaction.

A
  • raw experimental data
49
Q

a widely used method for determining the nitrogen content in organic compounds, including proteins.

A

Kjeldahl Analysis for Nitrogen and Protein

50
Q

__ __ __ (__), which also may be referred to as the __ __ __ (__), is used to determine if the standard deviation (σ) of a set of data is small or large when compared to the mean (µ). In other words, this can tell you how __ the average of your results is.

A
  • Relative standard deviation (RSD)
  • coefficient of variation (CV)
  • precise
51
Q

Closeness of a measured value to the true or accepted value.

A

accuracy

52
Q

Closeness of repeated measurements to each other.

A

precision

53
Q

How is accuracy assessed?

A

By comparing measured values to a known standard or accepted value.

54
Q

How is precision assessed?

A

By calculating the variability or spread of repeated measurements.

55
Q

What characterizes precise but not accurate measurements?

A

Measurements clustering closely together but consistently far from the true value.

56
Q

What characterizes accurate but not precise measurements?

A

Measurements consistently close to the true value but with significant variability.

57
Q

How were representative samples obtained in the deer kill case study?

A

The kidneys were dissected and removed for analysis because arsenic is rapidly eliminated from an animal through its urinary tract.

58
Q

What was the purpose of homogenizing the kidney samples in the deer kill case study?

A

To reduce the size of tissue pieces and homogenize the resulting laboratory sample.

59
Q

How were replicate samples defined in the deer kill case study?

A

Three 10-g samples of homogenized tissue from each deer were placed in porcelain crucibles.

60
Q

What process was used to dissolve the samples in the deer kill case study?

A

Dry ashing followed by incineration in a furnace set at 555°C for 2 hours, followed by the addition of HCl to produce arsenic acid (H3AsO4).

61
Q

What happens when arsine is bubbled into the solution in the cuvette?

A

It reacts with silver diethyldithiocarbamate to form a colored complex compound.

62
Q

It provides absorbance, which is directly proportional to the color intensity and concentration of the species responsible for the color.

A

spectrophotometer

63
Q

What level of arsenic in kidney tissue is considered toxic in the case study?

A

Levels above about 10 ppm (parts per million).

64
Q

What was the probable cause of death for the deer in the case study?

A

Ingestion of an arsenic compound.

Analytical Chemistry (7 decks)

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