EXPRESSING QUANTITIES & CONCENTRATIONS Flashcards
Acronym for the French word Systeme International d’ Unites
It is the standardized system of units
SI UNITS
Base unit of Length
Meter
Base unit of Time
Second
Base unit of Mass
Kilogram
Base unit of Temperature
Kelvin
Base unit of Electric Current
Ampere
Base unit of Luminious Intensity/ Light
Candela
Base unit of amt. of substance
Mole
It is the SI unit for the amount of chemical species
Associated with a chemical formula and Avogado’s number (6.00 x 1023)
The Mole
is the mass in grams of one mole of the substance
Calculated by summing the atomic masses of all the elements appearing in a chemical formula
Molar Mass (M)
Is an invariant measure of the amount of matter in an object
Mass
Is the force of attraction between an object and its surrounding
Weight
It is the one thousandth of a mole (1/1000 of a mole)
The Millimole
Number of moles of the solute species that is contained in one liter of the solution
Molar Concentration (Molarity M)
Is the total number of moles of solute in 1 L of solution
Analytical Molarity
AKA species molarity
Molar concentration of a particular species in solution at equilibrium
Equilibrium Molarity
Frequently used to express the concentration of commercial aqueous reagent
Weight Percent (w/w)
- Commonly used to specify the concentration of a solution prepared by diluting a pure liquid solute with another liquid
Volume Percent (v/v)
Often used to indicate the composition of dilute aqueous solution of solid reagents
Weight/Volume Percent (w/v)
is the negative logarithm (to the base 10) of the molar concentration of that species. Thus, for the species X
-p-value
is the mass of a substance per unit of volume - in SI Units, expressed as kg/L of g/mL
Density
Is the ratio of the mass of a substance to the mass of an equal volume of water
Specific Gravity
is the quantitative relationship among the amounts of reacting chemical species.
Stoichiometry
Used to measure the central value
AKA arithmetic mean or the average
Mean
Is the middle result when replicate data are arranged in increasing or decreasing order
Median
describes the reproducibility of measurements—in other words, the closeness of results that have been obtained in exactly the same way
Precision
indicates the closeness of the measurement to the true or accepted value and is expressed by the error
Accuracy
Is the difference between the measured value and the true value
Absolute Error
Is the absolute error divided by the true value
Relative Error
causes data to be scattered more or less symmetrically around a mean value
affects measurement precision
Random Error
causes the mean of a data set to differ from the accepted value
affects the accuracy of result
Systemic Error -
usually occur only occasionally, are often large, and may cause a result to be either high or low
Gross Error (Outlier)
is an occasional result in replicate measurements that differs significantly from the other result
outlier
TYPES OF ERROR IN EXPERIMENTAL DATA
Random Error
Systemic Error
Gross Error (Outlier)
SOURCES OF SYSTEMIC ERROR
Instrumental Errors
Method Errors
Personal Error
are caused by nonideal instrument behavior, by faulty calibrations, or by use under inappropriate conditions
Instrumental Errors-
arise from nonideal chemical or physical behavior of analytical systems
Method Errors
result from the carelessness, inattention, or personal limitations of the experimenter
Personal Error
are independent of the size of the sample being analyzed
Constant Errors
Decrease or increase in proportion to the size of the sample
Proportional Errors
If standard samples are not available, a second independent and reliable analytical method can be used in parallel with the method being evaluated - Independent method should differ as much as possible from the one under study
Independent Analysis
