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70 Cards in this Set
- Front
- Back
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Qualitative Analysis
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identification
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Quantitave Analysis
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relative amounts
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Calibration Equation
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Ca = k X
Ca = concentration of analyte k = proportionality constant X = measurment |
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Determinate Error
or Systematic Error |
errors with a definate value
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Indeterminate Error
or Random Error |
errors which fluctuate in a random fashion
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What are the sources of determinate error?
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instrument, method, and personal
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Accuracy
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agreement of a measurment/result (Xi) with its true value (Xt)
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What is accuracy dependent upon?
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knowing the true value
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Absolute Error Equation
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Er = Xi - Xt
Xi= measurment Xt= true value |
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Relative Error Equation
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Er = (Xi - Xt)/Xt
Xi= measurment Xt= true value |
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What methods can be used to detect error?
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standard samples, independent analysis,blank detmination, and varying sample size
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Stadard Samples
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known concentration
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Independent Analysis
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perform analysis using two different methods (gravimetric, volumetric, and spectrographic)
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Blank Determination
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run analysis without sample
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Proportional Error
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proportional to sample size
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What are some causes of indeterminate error?
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position of a meter needle relative to a fixed scale, liquid level in volumetric ware, or electronic noise
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Precision
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agreement between two or more measurments/results obtained in an identical fashion
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What is another name for a Gaussian Curve?
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normal error curve
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What detmines the width of the normal error curve?
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sigma
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Standard Deviation Equation
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S=
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Relative Standard Deviation Equation
(RSD) |
RSD=
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Coefficient of Variation Equation (CV)
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CV=
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Spread or Range
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numerical difference between the highest and lowest result
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Confidence limits Equation from Population Standard Deviation
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CL=
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Confidence Limits Equation from Sample Standard Deviation
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CL=
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How do you detmine if a outlier should be removed from a set of data?
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calculate Qexperimetal and compare to Qcritical. If Qexperimental is larger remove.
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Coprecipitation
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the precipitation of soluble impurities
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Surface Absorbtion
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surface contaminates (major problem with collidal precipitates)
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Occlusion
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rapid trapping of impurities
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Mixed Crystal Formation
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impurity becomes part of the crystalline lattice
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Mechanical Entrapment
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trapped impurities when several crystals grow together
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What are three major problems with the purity of a crystalline precipitate?
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occlusion, mixed crystal formation, and mechanical entrapment
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What are some ways to remove impurities?
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absorption, reprecipitation,and digestion
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Absorbtion
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remove by washing with a hot electrolyte solution (watch out for peptization)
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Reprecipitation
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re-dissolve and reform precipitate from a cleaner solution
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Digestion
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heating over a period of time.
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Collidial Precipitate
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large surface area to mass ratio
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Coagulation of Colloidal Particles
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attaching particles to each other to improve filtering
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What are the benifits of digestion?
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reduces surface charge and consequent double layer, increases particle size via bridging, and particle gain K.E. and overcome electric double layer
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What are the types of gravimetric analysis?
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precipitation, and gasification
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Precipitation Gravimetric Analysis
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the substance to be determined is isolated by formation of a known precipitate or a precipitate convertible to a known substance
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Gasification Gravimetric Analysis
What are the two types of gasification gravimetric analysis? |
the analysis involves producing a gas related to a sample
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Direct Gasification Gravimetric Analysis
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the determination of the mass of a gas produced by a chemical reaction
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Indirect Gasification Gravimetric Analysis
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the determination of the mass lost by a sample as aresult of production of a gas
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Gravimetric Analysis Mass % Equation
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Mass%=
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What are the desired properties of a precipitate?
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readily filtered and washed of contaminants, low solubility, unreactive with atmospere, known composition
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What are the physical properties of a colloid?
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they are smaller and gennerally more impure than crystalline precipitates
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What affects particle size?
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the relative supersaturation of the system at the moment, of precipitation
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Nuclei Formation
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minimum nuber of ions or molecules forming a second phase
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If Q is small the particles will be?
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crystalline
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If Q is large the particles will be?
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colloidal
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If s is small the particles will be?
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colloidal
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If s is large the particles will be?
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crystalline
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How can you lower the q value?
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dilute solution, slow rate of mixture, vigorous stirring
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What does solubility do with temperature increases?
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generally increases with temerature
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Mean
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the average
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Median
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the middle value for an odd set of data if arranged numerically
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Sample Varience
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standard deviation squared
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Peptization
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a coagulated colloid returns to its disperesed state
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Mixed Crystal Growth
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a type of coprecipitation in which a contaminat ion replaces an ion in the lattice of a crystal
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Nucleation
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process in which a minimum number of atoms, ions, or molecules join together to give a stable solid
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Counter-Ion Layer
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a layer of solution surrounding a colloidal particle within which there exists a quantity of ions suffecient to balance the charge on the surface particle
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Mother Liquor
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the solution from which a precipitate was formed
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Supersaturation
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a condition in which a solution temporarily contails an amount of solute that exceeds its equilibrium solubility
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Population Standard Deviation Equation
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=
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Standard Error of the Mean Equation
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=
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Q
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=
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wt/wt Equation
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=
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vol/vol Equation
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=
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wt/vol Equation
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=
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