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110 Cards in this Set
- Front
- Back
aliquot
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portion
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analyte
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substances being measured
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aqueous
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a solution of anything in water
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calibration curve
OR standard curve |
a graph of detector response as a function of analyte concentration
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composite sample
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a sample composed of multiple portions taken from different regions of a segregated heterogeneous material, which varies in composition in the same way as the material
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decant
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to pour off
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heterogeneous
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composition differs from region to region
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homogeneous
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composition is the same throughout
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interference
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occurs when a species other than the analyte increases or decreases the response of the analytical method and makes it appear that there is more or less analyte than is actually present
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masking
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the transformation of an interfering species into a form that is not detected
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qualitative analysis
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identifying what an unknown is
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quantitative analysis
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identifying how much unknown is present (analytical chemistry is concerned with this)
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quantitative transfer
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a complete transfer
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random heterogeneous material
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differences in composition occur randomly and on a fine scale
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random sample
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...is collected by taking portions from the desired number of segments chosen at random
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sample preparation
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transforming a sample into a state that is suitable for analysis
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sampling
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procuring a representative sample to measure
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segregated heterogeneous material
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large regions have obviously different compositions
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slurry
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a suspension of solid in a liquid
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species
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refers to any chemical of interest
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standard solution
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a solution containing a known concentration of a species used to generate a calibration curve
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supernatant liquid
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liquid above the packed solid
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abscissa
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the x-axis of a graph
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anhydrous
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the species does not have water in the crystal
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atomic mass
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the number of grams containing Avogadro's number of atoms
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concentration
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states how much solute is contained in a given volume or mass of solution or solvent
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density
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mass per unit volume
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electrolyte
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a substance that dissociates into ions in solution
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formal concentration
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the molarity of a strong electrolyte, emphasizes that the substance is converted into other species in solution
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formula mass
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the molecular mass of a strong electrolyte
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calorie
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the energy required to heat one gram of water from 14.5 to 15.5 degrees Celsius
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liter
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a commonly used unit for volume (the SI unit is the cubic meter) equal to 1/1000th of a cubic meter
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molality
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concentration expressed as moles of substance per kilogram of solvent (NOT total solution)
independent of temperature |
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molarity
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the number of moles of a substance per liter of solution
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mole
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Avogadro's number of particles (or anything else)
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molecular mass
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the sum of atomic masses of the elements in a molecule
the number of grams containing Avogadro's number of molecules |
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ordinate
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the y-axis of a graph
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ppb (parts per billion)
ppm (parts per million) |
an expression of composition that relates mass of substance to the total mass of the sample
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product
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species on the right side of a chemical equation
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reactant
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species on the left side of a chemical equation
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SI units
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Standard International units
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solute
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a minor species in a solution
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solvent
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the major species in a solution
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volume percent
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volume of solute per volume of total solution
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weight percent
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mass of solute per mass of total solution or mixture
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absorption
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the process in which a substance is taken into another
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acid wash
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replace low concentrations of cations on glassware with protons. Soak thoroughly cleaned glassware in 3-6 M HCl (in a fume hood) for >1 hour. Then, rinse well with distilled water, and soak in distilled water.
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adsorption
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the process in which a substance sticks to a surface
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ashless filter paper
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collect precipitate to be ignited, leaves little residue when burned
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buoyancy
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the upward force exerted on an object in a liquid or gaseous fluid
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buret
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a precisely manufactured glass tube with graduations enabling you to measure the volume of liquid delivered through the stopcock at the bottom
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calibration
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the process of measuring the actual quantity of mass, volume, force, electric current, etc. that corresponds to an indicated quantity on the scale of an instrument
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desiccant
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a drying agent
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desiccator
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a closed chamber containing a drying agent called a desiccator
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filtrate
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liquid that passes through the filter
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hygroscopic
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reagents which rapidly absorb moisture from the air. use procedure of weighing by difference
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ignition
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heating at high temperature over a burner or in a furnace
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meniscus
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a concave curve formed by most liquids. read volume at the bottom of meniscus using a meniscus reader
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mother liquor
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liquid from which a substance precipitates or crystallizes
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parallax
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the error that occurs when your eye is not at the same height as the liquid
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pipet
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glassware used to deliver a known volume of liquid
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tare
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the mass of an empty vessel
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volumetric flask
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glassware calibrated to contain a particular volume of solution at 20 degrees C when the bottom of the meniscus is adjusted to the center of the mark on the neck of the flask
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absolute uncertainty
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expresses the margin of uncertainty associated with a measurement
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accuracy
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describes how close a measured value is to the established "true" value
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relative uncertainty
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compares the size of the uncertainty with the size of its associated measurement
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characteristic
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a part of a logarithm, the number before the decimal point
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determinate error
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a.k.a. systematic error
arises from a flaw in equipment or design of an experiment. in principle, systematic error can be discovered and corrected |
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indeterminate error
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a.k.a. random error
arises from the effects of uncontrolled (and maybe uncontrollable) variables in the measurement |
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logarithm
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the base 10 logarithm of n is the number a, whose value is such that n=10^a
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mantissa
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a part of a logarithm, the number after the decimal point.
number of digits in the mantissa of log x = number of significant figures in x |
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natural logarithm
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the natural logarithm of the number x is the number y, whose value is such that x = e^y
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precision
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describes the reproducibility of a result
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standard state
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for solutes, the standard state is 1 M
for gases, the standard state is 1 bar for solids/liquids, the standard state is the pure solid or liquid |
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enthalpy change of reaction
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the heat absorbed or released when the reaction takes place under constant pressure
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exothermic
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negative enthalpy change of reaction
gives off heat |
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endothermic
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positive enthalpy change of reaction
requires heat to proceed |
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entropy
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measure of disorder in a substance
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Gibbs free energy
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determines whether or not a reaction will proceed
a reaction is favored if the change in gibbs free energy is negative |
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Le Chậtelier's principle
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states that a changed system proceeds back to equilibrium in a manner that tries to offset the change
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reaction quotient
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similar to equilibrium constant, but evaluated at any point in a reaction. At equilibrium, the reaction quotient is equal to the equilibrium constant
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solubility product
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the equilibrium constant for a reaction in which a solid salt dissolves to give its constituent ions in solution
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saturated solution
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a solution which contains as much solid as will dissolve in solution at the given conditions
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ion pair
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a closely associated pair of ions that behaves as one species in solution
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common ion effect
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a salt will be less soluble if one of its constituent ions is already present in the solution
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coprecipitation
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when a substance whose solubility is not exceeded precipitates along with another substance
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complex ions
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consist of two or more simple ions bonded to each other
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ligand
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any atom or group of atoms attached to the species of interest
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acid
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a substance that increases the concentration of hydronium ion when added to water
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base
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a substance that decreases the concentration of hydronium ion when added to water
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salt
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any ionic solid
formally, the product of an acid-base reaction |
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volumetric analysis
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procedures in which the volume of reagent needed to react with analyte are measured
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titrant
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the reagent solution used in a titration
(comes out of the buret) |
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equivalence point
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occurs when the amount of titrant added is the exact amount required for stoichiometric reaction with the analyte
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end point
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a sudden change in a physical property of a solution, what we see in a titration
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indicator
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a compound with a physical property (usually color) that changes abruptly near the equivalence point
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titration error
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difference between the end point and the equivalence point (unavoidable)
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blank titration
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contains all chemicals used in the titration except analyte. subtract from measurement to determine titration error
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primary standard
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a chemical pure enough to be weighed and used directly
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standardization
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process used to determine the concentration of a titrant. the titrant is then considered a standard solution.
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direct titration
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titrant is added to analyte until the reaction is complete
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back titration
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a known excess of one standard reagent is added to the analyte. then the excess reagent is titrated with a second standard reagent
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gravimetric titration
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titrant is measured by mass, not volume
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trace analysis
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analysis of species at ppm levels or lower
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strong acid
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an acid which dissociates completely or nearly completely into its ions in solution
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hydrolysis
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refers to a reaction with water
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weak acid
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an acid that is not completely dissociated
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conjugate acid-base pair
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related by the gain or loss of a proton
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weak electrolytes
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compounds that are only partially dissociated
dissociate more as they are diluted |
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buffer
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a mixture of an acid and its conjugate base
"A buffered solution resists changes in pH when acids or bases are added or when dilution occurs." |