chembio finals lec

Question 1

a measure of how close a measurement is to the true or (standard) value of the quantity being measured.

Answer 1

accuracy

Question 2

measure of how close a series of measurements are to one another.

Answer 2

precision

Question 3

agreement or closeness among measured values between runs.

Answer 3

reproducibility

Question 4

agreement or closeness among measured values within runs.

Answer 4

repeatability

Question 5

two components of precision

Answer 5

reproducibility and repeatability

Question 6

amount of error in your measurements. difference between the measured value and “true” value.

Answer 6

absolute error

Question 7

ratio of absolute error and the true (standard) value

Answer 7

relative error

Question 8

ways of expressing accuracy

Answer 8

absolute error (AE) and relative error (RE)

Question 9

average of different variations from a data set.

Answer 9

average deviation

Question 10

denoted by 𝜎 or s

Answer 10

standard deviation

Question 11

denoted by 𝜎 or s

Answer 11

variance

Question 12

a measurement of the spread between numbers in a data set

Answer 12

variance

Question 13

also known as the Relative Standard Deviation (RSD)

Answer 13

coeffecient variation

Question 14

the ratio of the standard deviation and the mean.

Answer 14

coeffecient variation

Question 15

difference between the lowest and highest values.

Answer 15

range

Question 16

ways of expressing precision

Answer 16

average deviation
standard deviation
variance
coefficient variation
range

Question 17

lowers the accuracy of the experiment.

Answer 17

error in measurements

Question 18

types of error

Answer 18

determinate/systematic error
indeterminate/random error
propagation of error/uncertainty

Question 19

errors that are known and controllable errors

Answer 19

determinate/systematic error

Question 20

nonrandom error that can be detected and corrected.

Answer 20

determinate/systematic error

Question 21

examples of determinate error

Answer 21

personal/operative, instrumental, and method errors

Question 22

faulty or uncalibrated equipment

Answer 22

intstrumental error (determinate)

Question 23

mathematical errors in calculations, prejudice in estimating measurements, incomplete drying, transfer solutions

Answer 23

personal/operative error (determinate)

Question 24

most serious error ex. Coprecipitation of impurities, slight solubility of the precipitate, incomplete reactions

Answer 24

method error (determinate)

Question 25

caused by uncontrollable or unknown fluctuations in variables that may affect experimental results.

Answer 25

indeterminate/random error

Question 26

arise from uncertainties in measurements

Answer 26

indeterminate/random error

Question 27

variation in line voltage, fluctuation of electrical current

Answer 27

instrumental error (indeterminate)

Question 28

misestimation of the meniscus, subjectivity in color changes

Answer 28

personal/operative error (indeterminate)

Question 29

variation in environmental conditions such as humidity, temperature, etc. during measurement and analysis.

Answer 29

method error (indeterminate)

Question 30

result due to several deviations of the instruments used in the conduct of measurement and analysis.

Answer 30

propagation of error/uncertainty

Question 31

defined as the effects on a function by a variable's uncertainty.

Answer 31

propagation of error/uncertainty

Question 32

also known as confidence interval

Answer 32

confidence limit

Question 33

shows how accurate an estimation of the mean is or is likely to be.

Answer 33

confidence limit

Question 34

range where the true (standard) value lies

Answer 34

confidence limit

Question 35

is an observation that lies an abnormal distance from other values in a random sample from a population.

Answer 35

outlier

Question 36

used to identify an outlier within a data set

Answer 36

q-test

Question 37

used to a determinate error; otherwise, it falls within the expected random error and should be retained

Answer 37

q-test

Question 38

suspected outlier is retained

Answer 38

qcalc < qtab

Question 39

suspected outlier is rejected

Answer 39

qcalc > qtab

Question 40

a standard solution is added to a solution of an analyte until the reaction between the analyte and reagent is judged to be complete

Answer 40

titration

Question 41

performed slowly by adding a standard solution from a buret or other liquid-dispensing device to a solution of the analyte until the reaction between the two is complete.

Answer 41

titration

Question 42

solution of accurately known concentration is added gradually to another solution of unknown concentration, until the chemical reaction between the two solutions is complete

Answer 42

standard solution

Question 43

the point in a titration which the amount of added standard reagents is exactly equivalent to the amount of analyte.

Answer 43

equivalence point

Question 44

point in a titration when a physical change occurs that is associated with the condition of chemical equivalence.

Answer 44

end point

Question 45

added to analyte solution to produce an observable physical change (the end point) at or near the equivalence point

Answer 45

indicators

Question 46

a highly purified compound that serves as a reference material in volumetric method.

Answer 46

primary standards

Question 47

compound whose purity has been established by chemical analysis and that serves as the reference material for a titrimetric method of analysis.

Answer 47

secondary standards

Question 48

a carefully weighed quantity of a primary standard is dissolved in a suitable solvent and diluted to an exactly known volume in a volumetric flask

Answer 48

direct method

Question 49

the titrant to be standardized is used to titrate a weighed quantity of a primary standard

Answer 49

standardization

Question 50

these substances react more completely with an analyte than do their weaker counterparts, and they therefore provide sharper endpoints.

Answer 50

standard solutions

Question 51

are prepared by diluting concentrated hydrochloric, perchloric or sulfuric acid.

Answer 51

standard solutions of acids

Question 52

seldom used because its oxidizing properties offer the undesirable side reactions.

Answer 52

nitric acid

Question 53

potent oxidizing agents and are very hazardous.

Answer 53

hot concentrated perchloric acid and sulfuric acids

Question 54

prepared from solid sodium, potassium, and occasionally barium hydroxides.

Answer 54

standard solutions of bases

Question 55

a weak organic acid or a weak organic base whose undissociated form differs in color from its conjugate base or its conjugate acid form.

Answer 55

acid/base indicator

Question 56

pH range of phenolphthalein

Answer 56

8-10, colorless (acid), red (base)

Question 57

compute the concentration of the acid from its starting concentration and the amount of base added

Answer 57

pre-equivalence

Question 58

the hydronium and hydroxide ions are present in equal concentrations, and the hydronium ion concentration is derived directly from the ion-product constant for water.

Answer 58

equivalence

Question 59

the analytical concentration of the excess base is computed, and the hydroxide ion concentration is assumed to be equal to or a multiple of the analytical concentration.

Answer 59

post-equivalence