chem lab final
Terms
undefined, object
copy deck
- colorimetry
- set of solutions of known concentrations is placed in a series of containers. unknown concentration is compared w/ calibrateion set
- beer's law
-
Absorbance=abc
a=prob. that substance absorbs light
b= path legnth of light thru sample
c= concentration of substance in solution - why aluminum expensive to produce
-
1. high grade bauxite deposits (needed) occur outside US
2. Hall-Heroult process extremely energy intensive - 2 uses for alum compound
-
1. phosphate removal agents in water and waste treatment plants
2. soap, plastics, cosmetics - presences of SO4, K+, Al3+, H2O
-
K+ : flame test; purple showed K+ was present
Al3+ : pH=1 to show Al present and acidic reaction
SO4: Barium w/ crystals showed insoluble SO4
H2O: flame->bubbling; crackling noise of evaporation was H2O was present - "like dissolves like"
-
polar compounds dissolve in polar solutions
nonpolar compounds dissolve in nonpolar solutions
ex.ammonia soluble in water (both polar) - kerosene, pentanol, ethanol, water
-
kerosene:w/ h2o=layered (nonpolar)
pentanol:w/kerosene=layered/mixture (nonpolar)
ethonal:w/kerosene=layered (polar)
water:w/ h2o=mixture (polar) - precipitation
- produces new compuond not soluble in aq. solution
- acid-base solution
- acid reacts w/ base to give water and salt
- complexation
- 1 or more coordinate covalent bonds produced during formation
- redox
- electrons are transferred from one species to another
- why water sample need to be spiked w/ MgEDTA?
- to ensure there is Mg in the water sample b/c Mg is needed for the reaction to occur
- ion exchange resin
- monovalent cations are exchanged w/ divalent cations
- how AA is carried out
- hallow cathode lamps emit monochromatic light, which corresponds to ^E of elements being analyzed. atoms in sample having electronic engery separation ^E will absorb the light and amount of absorbance is proportional to concentration of metal atoms in sample
- beer-lambert law
-
I(t)=I(o)(10^-abc)
I(o) is the intial light sorce and its decrease is proportional to the concentration of the metal in the sample - purpose of "standards" taht run as part of AA analysis?
- `the most accurate region of the calibration curve is between the max and min standard points
- problem w/ analyzing sample whose absorbance exceeds 1 absorbance unit?
- if the sample is above 1 au, there is little light transmitted for the PMT to detect.