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Analytical Chemistry > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

A vital step in any quantitative analysis

A

Select a Method

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2
Q

3 considerations in selecting a method

A
  1. The level of accuracy required
  2. The number of samples to be analyzed
  3. Complexity and number of components in the sample
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3
Q

the most important to be considered in the

selection

A

The level of accuracy required

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4
Q

True or False
Low reliability always requires a large invest
of time

A

False, high reliability

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5
Q

True or False

The selected method usually represents a
compromise between the accuracy required and the time and money available for the analysis

A

True

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6
Q

Consideration of selecting a method related to economic factors

A

The number of samples to be analyzed

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7
Q

What to do when there are many samples?

A

spend a significant amount of time in preliminary operations just assembling and calibrating instruments and equipment, and preparing a standard solution

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8
Q

What to do when there is only a single or few samples?

A

it is appropriate to select a procedure that avoids or minimizes such preliminary steps

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9
Q

Consideration of selecting a method which Influences the choice of method to some degree

A

Complexity and number of components in the sample

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10
Q

True or False

To produce meaningful information, an analysis must be performed on a sample that has a different composition as the bulk material from which it was taken.

A

False, same composition

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11
Q

Most difficult step in analysis and source of greatest error; must done carefully

A

Sampling

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12
Q

Challenges in sampling

A

Bulk samples

Heterogenous sample

Samples from biological sources

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13
Q

Give the types of samples to collect

A

Grab samples
Composite samples
In situ

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14
Q

A single sample or measurement taken at a specific time or over a short period as feasible

A

Grab samples

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15
Q

Involves taking several individual sampling units and mixing them before measuring, counting or analyzing the composite sample

A

Composite samples

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16
Q

measurement is taken in the same place the

phenomenon is occurring without isolating it from other systems or altering the original conditions of the test

A

In situ

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17
Q

True or False

The final analytical result will never be any more reliable than the reliability of the
sampling step.

A

True

18
Q

Is sample processing required when a sample is water withdrawn from a stream?

A

No, the pH of the sample can be measured directly.

19
Q

ground to decrease particle size, mixed to assure homogeneity, and stored for various lengths of time before the analysis begins

A

Solid laboratory sample

20
Q

the process by which ions, atoms or molecules adhere to the surface of the solid material

A

Adsorption

21
Q

the release of an adsorbed substance from a surface

A

Desorption

22
Q

What to do with samples with volatile solvent?

A

it must be kept in sealed containers

23
Q

solvents that are easily evaporated at normal temperatures

A

Volatile solvent

24
Q

involve mixing the sample and forming the solid material into a conical heap upon a solid surface followed by flattening the heap and dividing into four equal parts. two opposite quarters are taken as sample while the other two are discarded or set aside

A

Coning and quartering

25
Q
  • Involves dividing the sample into two approximate equal parts with the use of a riffler
  • Particularly useful with large samples which are normally more difficult to sub-sample
A

Riffling

26
Q

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

A

replication

27
Q

True or False

ideally, the solvent should dissolve the entire sample (not just the analyte) rapidly and completely

A

True

28
Q

Consideration when Preparing Solutions of the Samples

A

the end result of these conversions must leave the sample with a measurable property that is proportional to analyte concentration

29
Q

species other than the analyte that affect the final measurement

A

Interference/Interferents

30
Q

Should the interferences be removed? Why or why not?

A

Yes, Interferences must be removed before a measurement is to be done. Because they cause an error to the final measurement

31
Q

the measurement of the physical property is ______ proportional to the concentration

A

Directly

32
Q

Formula for conectration

A

𝐶 =𝑘𝑋

33
Q

What is k in the formula? Thank

A

k is the proportionality constant

34
Q

The process of determining k

A

Calibration

35
Q

Ordinarily a simple and straightforward task particularly with modern calculators and computers

A

Calculating Results

36
Q

computations are based on:

A
  1. the raw experimental data collected in the
    measurement step
  2. the stoichiometry of the chemical reaction
    upon which the analysis is based
  3. instrumental factors
37
Q

analytical results are incomplete without ______

A

an estimate of their reliability

38
Q

A sampling technique in which each member of the subset has an equal probability of being chosen

A

Random sampling

39
Q

a non-probability sampling technique in which the sample members are chosen only on the basis of the researcher’s knowledge and judgment

A

Judgmental sampling

40
Q

a type of probability sampling method in which sample members from a larger population are selected according to a random starting point but with a fixed, periodic interval

A

Systematic sampling

41
Q

a method of sampling that involves the division of a population into smaller sub-groups known as strata

A

Stratified sampling

42
Q

a method adopted by researchers where they collect market research data from a conveniently available pool of respondents

A

Convenience sampling

Analytical Chemistry (1 decks)

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