chapter 2-Terms Flashcards
It is used in classifying Chemicals
Reagent-grades
Why are Raegent-grades used in classifying Chemicals?
It conforms to the minimum standards set forth by the Reagent Chemical Committee of the American Chemical Society (ACS) and are used whenever possible in analytical work.
It is reagents that have been carefully analyzed by the supplier, and the results are printed on the container label.
Primary standard reagents
The (blank) is an excellent source for primary standards.
The National Institute of Standards and Technology (NIST)
Complex substances that have been exhaustively analyzed
Reference Standards
What are the chemicals that have been prepared for a specific application?
Special-Purpose Reagent Chemicals
Give two experiments to when the Special-Purpose Reagent Chemicals are used
Spectrophotometry and High-performance liquid chromatography
It is usually performed in duplicate or triplicate
Chemical Analysis
Why is evaporation frequently difficult to control?
It is because of the tendency of some solutions to overheat locally.
When does the bumping occur?
When a sample boils rapidly
If the bumping is sufficiently vigorous, what can it possibly cause?
Partial loss of the solution
How is the wet ashing done?
by adding sulfuric acid and heating to the appearance of sulfur trioxide fumes (in a hood)
Organic constituents can be frequently eliminated from a solution via?
Wet ashing
what does analytical balance do?
used to measure masses with high accuracy.
It is the less accurate balances that are also used for mass measurements when the demands for reliability are not critical
Laboratory balances
What is an analytical balance
An instrument for determining mass with a maximum capacity that ranges from 1 g to a few kilograms with a precision of at least 1 part in 10^5 at maximum capacity.
define Macro balances
It is the most common analytical balance that has a maximum capacity ranging between 160 and 200 g.
How many does the Semimicroanalytical balances measure?
it has a maximum loading of 10 to 30 g with a precision of +-0.01 mg
Give the capacity to measure of the microanalytical balance
it has a capacity 1 to 3 g and a precision of +- 0.001 mg.
What is the equal-arm balance
simplest and earliest method of weighing.
The downside of using an equal-arm balance
It was tedious and time consuming
When did the first single-pan analytical balance appeared on the market?
1946
What kind of balance replaced the single-pan balance?
The electronic analytical balance
How, or what supports or levitates the cylinder, the pan, the indicator arm, and whatever load is on the pan?
It is because of the electric current in the coil which produces a magnetic field
What is a servo system?
It is a device in which a small electric signal causes a mechanical system to return to a null position.
In each, the pan is tethered to a system of constraints known collectively as a what??
cell
What is Taring?
It is the process of setting a balance to read zero in the presence of an empty sample container (tare)
What is a tare
the mass of an empty sample container
What does W1 represent?
It represents the corrected mass of the object
What does W2 represent?
It represents the mass of the standard masses
What does d-air represent?
The density of air displaced by the masses and objects
What does d-obj represent?
The density of the object
What does d-wts represent?
The density of the masses
