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Chem Lab Terms
| Term | Definition |
|---|---|
| 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 |
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jpf11230
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