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70 Cards in this Set

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