basic operations in analytical chemistry Flashcards
what does analytical balance measure
it is used to measure masses with high accuracy
what are the 3 types of analytical balance (and its capacity)
macrobalances (160-200g)
semimicroanalytical (10-30g)
microanalytical (1-3g)
true or false
center the load on the pan in the analytical balance
true
true or false
adjust the analytical balance yourself if it needs adjustment
false - ask an instructor
true or false
keep the balance scrupulously clean only
false - and it’s case too
true or false
always allow an object to cool down to room temperature before weighing it in the analytical balance
true
why do we use tongs, finger pads or a glassine paper strip to handle dried objects
to prevent transferring moisture to them
what equipment do you use for removing spilled material or dust in the analytical balance
camel’s hair brush
low precision balance should be used when …
high sensitivity is not required
it is well- used for larger, messier samples that are raw or need to be processed.
top-loading balance
what is being cooled in a desiccator before weighing
oven-dried sample or reagents
true or false
failure to allow sufficient time for a heated object to return to room temperature is the most common source of the problem
true
attempts to weigh an object whose temperature is different from that of its surrounding will result in…
significant error
desiccator
keep samples dry while they are cooling and before they are weighed in
muffle furnace
ignite sample to high temperatures
(either to convert precipitates to a weighable form or
burn organic materials prior to inorganic analysis)
oven
dry samples prior to weighing
hood
trap and exhaust vapors, gases and nanoparticles
when do we use fume hood
when chemicals or solutions are to be evaporated
wash bottles
wash precipitates
it is used for quantitative transfer of precipitates and solutions
wash bottle
centrifuge
it is where blood may have to be separated into fractions such as serum or plasma and proteins may have to be separated by precipitation followed by centrifuging
it has many useful applications, particularly in clinical laboratory
centrifuge
it permit the transfer of accurately known volumes from one container to another.
pipets
what are the types of pipets
- volumetric/ transfer
- measuring/ graduated
- mohr
- serological
true or false:
the final volume of solution must be blown out from the tip to deliver the calibrated amount.
true
identify the available capacity based on the pipets
volumetric-
mohr-
serological-
volumetric- 1-200 mL
mohr- 1-25 mL
serological- 0.1-10 mL
this pipet delivers a single and fixed volume. used for accurate measurement since it is designed to deliver only one volume and s calibrated at that volume
volumetric pipet
this pipet are straight- bore pipets that are marked at different volume intervals.
measuring pipets
difference between serological and mohr pipet
seriological - blown out
mohr - not blown out like volumetric
true or false:
when transferring liquid using the volumetric pipet, it is important to use your thumb to stop the flow of liquid
false- use your index finger instead because thumb tends to have larger areas of contact = less control of releasing pressure
it is a common yet essential laboratory instrument used to accurately and precisely transfer volumes of liquid in the microliter range
micropipettes
this pipet is available in single-
channel and multi- channel variants. it is also available in different designs and sizes
micropipettes
which instrument is commonly used in titrations
burets
they are used for the preparation of
standard solutions and for the dilution of samples to a fixed volume prior to taking aliquots with a pipet.
volumetric flask
Aliquot
fraction of solution
this equipment is considered more accurate and precise for measurement purposes than flasks and beakers but should not be used for volumetric analysis
graduated cylinder
a marked curvature at the top surface of a liquid confined in a narrow tube
meniscus
meniscus:
* Clear liquid –
* Colored and opaque liquid –
- Clear liquid – lower meniscus
- Colored and opaque liquid – upper
meniscus
is a condition that causes the
volume to appear smaller than its actual value if the meniscus is viewed from above and larger if the meniscus is viewed from below.
parallax
