Quant Chem - Test 1

Front 1

sampling

Back 1

the first step in any chemical analysis - procuring a representative sample to measure

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homogeneous

Back 2

composition is the same throughout (Ex. chocolate bar)

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heterogeneous

Back 3

composition differs throughout (Ex. chocolate bar with nuts)

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decanted

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to poured off

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supernatant

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liquid above the packed solid

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analytes

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substance being measured

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slurry

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suspension of solid in a liquid

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aliquots

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the portions that are measured from the concentration of an analytes

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Molarity (M)

Back 9

the moles of solute /
L of solution

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molality (m)

Back 10

moles of solute /
kg of solvent

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solute

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minor species in solution

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solvent

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major species in solution

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concentration

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how much solute is contained in a given volume or mass of a given solute or solvent

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electrolyte

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substance that disassociates into ion in solution

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formal concentration (F)

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molarity of a strong electrolyte

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formula mass (FM)

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molecular mass of a strong electrolyte

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weight percent

Back 17

(mass of solute / mass of total solution) X 100

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volume percent

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(volume of solute / total volume of solution) X 100

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parts per million (ppm)

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(mass of substance / mass of sample) X 10^6

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parts per billion (ppb)

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(mass of substance / mass of sample) X 10^9

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dilution formula

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M conc X V conc =
M dil X V dil

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abscissa

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x-axis

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ordinate

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y-axis

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Lab notebook must:

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1) state what was done
2) state what was observed
3) be understood by someone else

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parallax

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the error that occurs when you eye is not at the same height as the liquid.

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meniscus

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a concave surface of liquids

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precision

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the ability to reproduce with the same results

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accuracy

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the difference between the actual and stated volume delivered.

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adsorption

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the process in which a substance sticks to a surface

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absorption

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the process in which a substance is taken into another

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mother liquor

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liquid from which a substance precipitates or crystallizes

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filtrate

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liquid that passes through a filter

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standard solutions

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contain known concentrations

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hygroscopic reagents

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reagents which rapidly absorb moisture from the air

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dessiccator

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a closed chamber containing a drying agent called a desiccant

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calibration

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the process of measuring the actual quantity of measurement that corresponds to an indicated quantity on the scale of an instrument.

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systematic error

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also called determinate error arises from a flas in equipment or the design of the experiment

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random error

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also called indeterminate error arises from the effects of uncontrolled variables in the measurement

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precision

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reproductibility of results

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accuracy

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how close a measured value is to the "true" value

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absolute uncertainty

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expresses the margin of uncertainty associated with ta measurement

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relative uncertainty

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compares the size of the absolute uncertainty with the size of its associated measurement

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gaussian distribution

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more times the experiment is repeated the more closesly the results approach an ideal smooth curve

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mean (x)

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also called average

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standard deviation (s)

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measures how closely the data are clustered about the mean.

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degrees of freedom

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n-1; quantity minus 1

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variance

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square of the standard deviation

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confidence interval

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an expression stating that the true mean (μ) is likely to lie within a certain distance from the measured mean (x)

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student's t

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a statistical tool used most frequently to express condience intervals and to compare results from different experiements.

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t-test

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to compare one set of measurements with another to decide whether or not they are "the same"

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F test

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tells us whether two standard deviations are "significantly" different from each other

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Q test

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to help decide whether to retain or discard a questionable datum

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determinate

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represents matrix (eh - fg)

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standard solutions

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solutions containing known concentrations of analyte

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blank solutions

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solutions containing all reagents and solvents used in analysis, but no delibertly added analyte

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linear response

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the corrected analytical signal is proportional to the quantity of analyte

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linear range

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the analyte concentration range over which response is proportional to concentration

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dynamic range

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concentration range over which there is a measurable response to analyte, even if the response is linear

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Quality Assurance

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what we do to get the right anser for our purpose

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use objective

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states purpose for which results will be used

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specifications

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stating how good the numbers need to be and what precautions are required in the analytical procedure

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false positive

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says that the concentration exceed the legal limit, when in fact, the concentration is below the limit

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false negative

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says that the concnetration is below the limit when it is actually above the limit

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selectivity

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being able to distinguish analyte from othe species in the sample

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sensitivity

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capability of responding reliably tand measurably to changes in analyte concentration

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method blank

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sample containing all components except analyte

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reagent blank

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similar to method blank, but has not been subjected to all sample preparation procedures

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field blank

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similar to method blank, but it has been exposed to the site of sampling

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matix

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to refer to everthing else in the sample other than the analyte

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spike

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also called fortification, known quantity of anlyte added to a sample to test whether the response to a sample is the same as that expected from the calibration curve

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calibration check

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analyze solutions formulated to contain known concentrations of analyte

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performance test samples

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also called quality control samples; measure to help eliminate bias introduced by the analyst knowing the concentration of the calibration check sample

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standard operating procedure

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what steps will be taken and how they will be carried out are the bulward of quality assurance

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assessment

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the process of (1) collecting datat to show that analytical procedures are operting within specified limits and (3) verifying the final results meet use objectives

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method validation

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process of proving that an analytical method is acceptable for its intended purpose

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specificity

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the ability of an analytical method to distinguish the analyte from everything else that might be in the sample

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linearity

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how well a calibration curve follows a straight line

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range

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the concentration interval over which linearity, accuracy, and precision are all acceptable

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detection limit

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smallest quantity of analyte that is "significantly different" from the blank

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reporting limit

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the concentration below which regulatory rules say that a given analyte is reported as "not detected"

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robustness

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the ability of an analytical method to be unaffected by small, deliberate changes in operating parameters

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standard addition

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known quantities of analyte are added to the unknown

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matrix effect

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a change in the analytical signal caused by anything in the sample other than the analyte

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interval standard

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known amount of a compound, different from analyte, that is added to the unknown