U1- Stoichiometry, Gravimetric Analysis and Gases Flashcards
limiting reactant
reactant that is completely consumed in reaction
gravimetric analysis
technique which the amount of an analyte can be determined through the measurement of mass before and/or after a physical or chemical change
precipitate
A solid that is formed in a reaction between two dissolved substances or gases
analyte
The ion or solution being analysed
residue
The solid remaining in the filter paper during filtration
filtrate
The liquid that passes through the filter paper during filtration
dry to constant mass
A process in which a solid is weighed, dried and re-weighed until the mass no longer changes. This ensures that all of the excess water has been completely removed.
validity
whether evidence supports the argument
sources of error in a gravimetric analysis (6)
solubility (or insolubility) of precipitate
variation of solubility w temp
losses through splashes, inefficient rinsing and inefficient filtering
extend of drying of solid
is all of the active ingredient precipitated out? (solved by adding excess reagent)
measurement errors
how could solubility of precipitate of gravimetric analysis impact results
incomplete precipitation –> lower experimental content then expected –> decreased measurement mass
how could variation in solubility with temperature impact gravimetric analysis results
incomplete precipitation –> lower experimental content then expected –> decreased measurement mass
how could losses thru splashing, inefficient rinsing and inefficient filtering impact gravimetric analysis results
incomplete transfer of precipitate –> lower exp content than expected –> decreased measured mass
how could the extent of drying the solid impact gravimetric results
water in precipitate –> higher experimental content than expected –> increased measured mass
how could not all the active ingredient not being precipitated out impact results of the gravimetric analysis
incomplete precipitate –> lower exp content than expected
how could not all the active ingredient not being precipitated out impact results of the gravimetric analysis
incomplete precipitate –> lower exp content than expected
how could measurement errors impact gravimetric analysis results
random outcome due to inaccuracies w measurements of mass, volume ect
properties of ideal gases
constant and random motion,
very far apart
negligible attractive or repulsive forces bw particles
collisions bw particles are perfectly elastic (X loss of k nrg)
pressure conversions:
kPa to mmHg to atm
100kPa = 750mmHg = 0.987atm
Boyle’s Law
for a fixed amount of gas at constant temperature, pressure is inversely proportional to volume.
P1V1 = P2V2
Charles Law
For a given amount of gas at constant pressure, volume is directly proportional to the absolute temperature
V1/T1 = V2/T2
standard temperature and pressure (STP)
0C / 273K
100kPa
standard lab conditions (SLC)
25C / 298K
100kPa
molar gas v= 22.7L/mol
molar gas volume
equal volumes of all gases measured at the same temperature and pressure contain the same number of particles
why does the solution (silver nitrate) you mix with the analyte need to be in excess
eg Ag+(aq)+ Cl-(aq)> AgCl(s), add Silver Nitrate in excess to mineral water being analysed.(analysis of chloride ions)
so that there are more than enough silver ions to precipitate all of the ions out of the solutions
atom economy
Mr of desired products/ Mr of total products x100
% yield
actual yield/ theoretical yield x100
