Gravimetric Analysis Flashcards
what is gravimetric analysis?
a method to determine the mass of an element or compound in a substance
what are weighing boats used for?
to measure substances on a balance without contamination
what does the tare function on a balance do?
sets the balance to zero with a container on the pan
what is weighing by difference?
weigh the weighing boat after adding substance, remove substance to destination and weigh the empty boat
the difference is the mass of the substance
what does weighing approximately accurately mean?
weigh close to the calculated mass, but record the exact value used
what does heating to a constant mass involve?
weigh the sample
heat to remove moisture
cool in a desiccator
reweigh
repeat until mass is constant
what is the purpose of a desiccator?
prevent reabsorption of water while cooling
how is mass determined in gravimetric analysis?
by converting the substance into a compound of known composition that can be isolated and weighed
what are the key requirements for a product in gravimetric precipitation?
low solubility
large enough particle size for filtration
thermal stability
why must gravimetric procedures be done carefully?
to ensure complete transfer of material and accurate weighing of dried products
what happens during a precipitation and filtration gravimetric method?
two solutions are mixed
solid forms
filter
test filtrate for completeness
dry solid to a constant mass
how do you ensure a precipitation reaction has gone to completion?
add an excess of one reactant and test the filtrate for remaining ions
what is volatilisation?
heating a substance to evaporate volatile components (water), causing a loss in mass
what is the final step after heating during volatilisation?
heat to constant mass, cool, and then record the final mass
