MIDTERMS Flashcards
(31 cards)
use to judge the quality of experimental measurements are many.
Statistical calculations
Impossible:
Possible:
Impossible:
The analytical results are free of errors or uncertainties.
Possible:
Minimize these errors and estimate their size with acceptable accuracy.
Chemists usually carry _____ of a sample through an entire analytical procedure
two to five portions (replicates)
Mean, arithmetic mean, and average (X) are synonyms for the quantity obtained by dividing the sum of replicate measurements by the number of measurements in the set
Mean
The _____ is the middle result when replicate data are arranged in order of size.
For an odd number of data points, the _____ can be evaluated directly.
For an even number, the _____ of the middle pair is used.
Median
_____ describes the reproducibility of measurements; the closeness of results to each other.
* _____ is determined by repeating the measurement on replicate samples.
* Three terms to describe the ____ of a set of replicate data: standard deviation, variance, and coefficient of variation.
Precision
Three terms to describe the precision of a set of replicate data: ______, _____, and _____.
standard deviation, variance, and coefficient of variation.
_____ is the closeness of results to others that have been obtained in exactly the same way.
Precision
_____ indicates the closeness of the measurement to its true or accepted value and is expressed by the error.
_____ measures agreement between a result and its true value.
Accuracy
The _____ in the measurement of a quantity x₁
absolute error E
is a more useful quantity than the absolute error.
is also expressed in parts per thousand (ppt).
Relative Error
a finite number of experimental observations is called a _____
sample of data
Statisticians call the theoretical infinite number of data a _____, more specifically a parent population, or a universe, of data.
population
is a measure of the precision or scatter of a population of data
Population Standard Deviation (σ)
Another term to describe the precision of a set of replicate results.
It is the difference between the largest value in the set and the smallest.
Spread or Range (w)
is defined as the mass relationships among reacting chemical species.
Stoichiometry
gives the simplest whole-number ratio of atoms in a chemical compound.
empirical formula
specifies the number of atoms in a molecule.
molecular formula
provides additional information.
structural formula
is a statement of the combining ratios, or stoichiometry (in units of moles), among the reacting substances and their products.
balanced chemical equation
This reactant limits the chemical reaction.
It is also called _______.
It is completely used up in the reaction, and thus determines when the reaction stops.
Limiting Reactant / limiting reagent
Most of the solutes we discuss are ______, which form ions when dissolved in water (or certain other solvents) and thus produce solutions that conduct electricity.
electrolytes
______ electrolytes ionize essentially completely.
strong
____ electrolytes ionize only partially.
weak
