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Chem Lab Terms

TermDefinition
Chelate a compound containing a ligand (typically organic) bonded to a central metal atom at two or more points.
complexometric titration is a form of volumetric analysis in which the formation of a colored complex is used to indicate the end point of a titration.
direct titration a way to determine the contents of a substance quantitatively.
displacement titration Here the analyte is treated with an excess of a second metal bound to EDTA. The analyte ion displaces the second metal from the EDTA complex
Lewis acid electron pair acceptors
Lewis base electron pair donors
Ligand an atom or group of atoms bound to whatever atom you are interested in
monodentate ligand ligand that bonds to a metal ion through only one atom
multidentate ligand binds to the metal ligand through more than one ligand atom
Aliquot portion that represents a whole
aliquot factor portion of total solution
analyte substance that is undergoing analysis (substance being measured)
analytical concentration concentration when you weigh something and dissolve it→ the total number of moles in
equilibrium concentration the actual concentration
density m/v
molarity moles solute/ L solution
molecular weight molar mass ( mass of a molecule) calculated as the sum of the mass of each constituent atom multiplied by the number of atoms of that element in the molecular formula
weight percent weight solute/ mL sample
qualitative analysis identifying what is in an unknown
quantitative analysis identifying how much is present
gravimetric analysis mass of product is measured to determine how much unknown was present
analytical balance measure to 4 decimal places
buret used to titrate→ goes to 4 s.f. measures in mL
desiccant drying agent in dessicator
desiccator closed chamber containing drying agent—to keep samples dried
direct weighing place directly on balance
hygroscopic absorbs/ attracts moisture from air
indirect weighing weigh by difference—do not weigh onto balance
meniscus curvature of liquid caused by surface tension
pipet used to transfer known amount of liquid- can go to 4 s.f.
tare 0 a balance
top-loading balance measures to 2 decimal places
volumetric flask calibrated to contain certain vol of liquid at 20 degrees celcius when bottom of meniscus in in the right spot
parallax error error that occurs when your eye is not at the same height as the meniscus
accuracy difference between delivered and desired volume
determinate error repeatable if measurement made same way (correctable)
indeterminate error (random error)- from experiment
precision reproducibility of replicate deliveries
degrees of freedom where n is number of data points
confidence interval range of values in which there is a specified probability of finding the true mean
Gaussian distribution characterized by a mean and standard deviation—mean is center of distribution and standard deviation is width→ (bell shaped curve)
student’s t test statistical tool used to express confidence intervals and to compare results from different experiments
Absorbance→ most useful quantitity for chemical analysis (A)—higher the absorbance
absorbance spectrum → graph showing how A (or epsilon) varies with wavelength Beer's law→
calibration curve→ absorbance at one wavelength is plotted against different concentrations in a series of standards
cuvet→ cell which has flate
molar absorptivity→ symbolized by epsilon
spectrophotometry→ the use of electromagnetic radiation to measure chemical concentrations
transmittance → the fraction of incident light that passes through a sample T=(P/Po)
wavelength→→ crest- to- crest distance between waves
Aliquot portion that represents a whole
aliquot factor portion of total solution
analyte substance that is undergoing analysis (substance being measured)
analytical concentration concentration when you weigh something and dissolve it
equilibrium concentration the actual concentration
density m/v
molarity moles solute/ L solution
molecular weight molar mass ( mass of a molecule) calculated as the sum of the mass of each constituent atom multiplied by the number of atoms of that element in the molecular formula
weight percent weight solute/ mL sample
qualitative analysis identifying what is in an unknown
quantitative analysis identifying how much is present
gravimetric analysis mass of product is measured to determine how much unknown was present
analytical balance measure to 4 decimal places
buret used to titrate
desiccant drying agent in dessicator
desiccator closed chamber containing drying agent—to keep samples dried
direct weighing place directly on balance
hygroscopic absorbs/ attracts moisture from air
indirect weighing weigh by difference—do not weigh onto balance
meniscus curvature of liquid caused by surface tension
pipet used to transfer known amount of liquid- can go to 4 s.f.
tare 0 a balance
top-loading balance measures to 2 decimal places
volumetric flask calibrated to contain certain vol of liquid at 20 degrees celcius when bottom of meniscus in in the right spot
parallax error error that occurs when your eye is not at the same height as the meniscus
accuracy difference between delivered and desired volume
determinate error repeatable if measurement made same way (correctable)
indeterminate error (random error)- from experiment
precision reproducibility of replicate deliveries
relative error relative uncertainty? (Absolute uncertainty/magnitude of measurement)
relative precision (rsd) measurement of how close measurements are to each other
systematic error error in process or equipment
degrees of freedom (n-1)
confidence interval range of values in which there is a specified probability of finding the true mean
Gaussian distribution characterized by a mean and standard deviation—mean is center of distribution and standard deviation is width (bell shaped curve)
standard devation measure of width of distribution
relative standard deviation std deviation devided by mean
pooled standard deviation pooled standard deviation to make use of multiple sets of data
Grubbs test test for an outlier
t statistic ratio of the departure of an estimated parameter from its notional value and its standard error
p value tells you if you can reject or accept your null hypothesis
F test to test if variances from two things are equal
student’s t test statistical tool used to express confidence intervals and to compare results from different experiments
variance square of the standard deviation
back titration excess of a standard reagent is added to analyte
blank titration contains everything except the analyte helps us see titration error
end point sudden change in physical property of solution
equivalence point when the moles of titrant moles of analyte in their stoichiometric relationship
indicator compound with a property that changes abruptly when titration is complete
primary standard pure enough to weigh and use directly for number of moles
standard solution solution containing known quantity of analyte
standardization titrating to determine concentration of titrant
titrant known reagent solution
titration increments of a known reagent are added to the analyte
titration error difference between endpoint and equivalence point
volumetric analysis volume of known reagent required for complete reaction with analyte by a known reaction is measured
indicator error dif btwn observed and true equivalence point
primary standard acids and bases acid
KHP bases
Na2CO3 and THAM
Kjeldahl Nitrogen determination one of the most widely used methods for determining
nitrogen in organic substances the solid is digested in boiling sulfuric acid to convert nitrogen into ammonium
Chelate compound containing a ligand (typically organic) bonded to a central metal atom at two or more points
complexometric titration for of volumetric analysis in which the formation of a colored complex is used to indicate the endpoint of a titration
direct titration way to determine the contents of a substance quantitatively
displacement titration analyte is treated with excess of a second metal bound to EDTA. The analyte ion displaces the second metal from the EDTA complex
indirect titration another name for a back titration
formation constant equilibrium constant for reaction of a metal with a ligand. Also called stability constant
Lewis acid electron pair acceptor
Lewis base electron pair donors
Ligand atom or group of atoms bound to whatever atom you are interested in
masking agent prevents impurities from reacting with the precipitant
monodentate ligand ligand that bonds to a metal through only one atom
multidentate ligand binds to the metal ligand through more than one ligand atom
adsorption indicator used in Fajans titration
argentometric titration titrations iinvolving Ag+
Fajans titration adsorption of a colored indicator on the precipitate at the end point
Mohr titration determination of a chloride by precipitation titration with silver nitrate
Vollhard titration formation of a soluble
iodimetry when a reducing analyte is titrated wIth iodine
iodometry titration Of iodine produced when oxidizing analyte is added to excess I-
Spectroscopy Absorbance most useful quantitity for chemical analysis (A)—higher the absorbance
absorbance spectrum graph showing how A (or epsilon) varies with wavelength
Beer's law dependence on concentration and path length
calibration curve absorbance at one wavelength is plotted against different concentrations in a series of standards
cuvet cell which has flate
molar absorptivity symbolized by epsilon
spectrophotometry the use of electromagnetic radiation to measure chemical concentrations
transmittance the fraction of incident light that passes through a sample TEquals(P/Po)
wavelength crest- to- crest distance between waves
Created by: jpf11230