Chap 6 & 7 Flashcards
SP. 6.1b. I.Describe how TITRATION used to obtain [ion] is relevant to TDS measurement. Some titration examples
A known volume V1 is titrated by a standard of Known volume V2 and [M2] to the endpoint (visual) which indicates the reaction is at the equilibrium and the [M1] is determined by stoichiometry. if the stoichiometry is 1:1, therefore, M1=(M2V2)/V1
Some eg. of this titration:
- AB: [UNK acid], P, M points are used to determine [Alk] and [HCO3-] & [CO3]
- Redox: the titration of residual Chloride awa COD involve in redox titration.
- pptn: the titration for Chloride and AgNO3
- complex formation: titration of Hardness, Calcium and Magnesium
SP.6.1b II. Describe how ION Chromatography (IC)
the use of an ion exchange column to analyze for anions and involving a conductivity detector.
Most [anion] can be defined thru calibration curve except CO3, HCO3 because of suppressor
SP6.1b III. Atomic Absorption Analysis (AA)
Light is directed thru the sample and the attenuation(sự làm yếu) of the intensity is used to determine the concentration of the Unknown when calibration curve is determined
Eg. sodium, calcium, copper & zinc
SP6.1b IV.Atomic Emission Analysis (ICP)
The wavelength and the intensity of the emitted light is used to determine the identity and [UNK} while calibration curve obtained
Eg. Most metals
SP6.1 V.Potentiometric Analysis (Ion-selective Electrode or ISE)
An electrode is designed that measure the activity of a particular ion via a reaction at either an anode or at a cathode. The calibration curve obtained to determine the [UNK]
Eg. Cl, F, ammonium, hydronium ( OH), NH4, metals such as silver
SP.6.2.c 3 methods used to obtain TDS
Evaporation/ weighing
Conductivity
Ion Analysis
TDS - Evaporation/ Weighing method
Known Vsample placed in a preweighed container and then dried at 105C. TDS in mg/L at a constant weight= The difference in weight/ Vsample.
Advs: cheap, not required lots of work, time-consuming
Disadvs: significant error from some substances are volatile and some change form when heated and some organics are not volatile leading to confusion between TDS and Dissolved Organics
TDS - Conductivity
Compare the measured conductivity value of the sample to the standard NaCl(ap). The TDS is reported as though the sample was also made up of NaCl
Advs: cheap, easy to use, quick, does not require a lot of skill
Dis: values are only approximate
TDS - Ion Analysis
individual ion are analyzed using a variety of technique ranging from the very expensive ICP MS to relatively inexpensive ISE, total TDS = all [ion] in mg/L
Dis: time consuming, expensive
Advs: very accute
SP.6.3b. Describe how molecules absorb waves in the
Microwave: molecules rotate
IR: molecules vibrate
VIS or V: electronic excitation occur
gamma ray: inner shell electrons are excited
6.3d Define T and %T
T: the amount of light transmitted thru a solution.
%T: the percentage of light transmitted by the substance relative to the reference blank
Value of Absorbance
A= 2 - log %T
6.4d. Analyte
the components of a sample being determined
6.4d. Blank solution
containing reagents and solvents, but NO analyte
6.4d. Standard solution
a solution in which the concentration of a solute is known with high reliability
6.4d. Why Fe colorimetric Analysis needs both blank and set of standards
- blank: used to calibrate the spectrometer to zero that means t
standard: used to predict the relationship btw absorbance and [ ]
6.4e. 4 Advantages of ICP instruments
- can determine many elements in an analysis
- large liner range & low detection limits
- very few interferences (ionization, chemical & interelement interferences are eliminated
- can detect elements that thermally decomposite at the lower temps of the flames used in AA.
6.4e. linear range
concentration range where the measured absorbance follows Beer’s law ( linear relationship btw absorbance and [ ] : A=Ebc
6.5b. by the graph, distinguish btw interpolation and extrapolation
both: involved in drawing a best fit line in order to obtain values that are not measured
Interpolation: keeps the best fit line btw the highest (8) and lowest (2) measured values
Extrapolation: goes beyond the highest and lowest measured values
6.5b. II. Linear and non-linear
Linear: where the best fit line follows a straight line. on the graph, linear from 2-8 and may be extrapolated till it reaches a max Ab (same subsequent [ ]).
Non linear: where the best fit is no longer linear
6.5b. III. Data point (0,0) is not included
the point could not be measured. the increase and decrease are unavoidable called NOISE. This due to instrumental errors.
6.6a. Blanks
in IC, Anions are separated by ion exchange and are detected by conductivity
6.6c. Explain a suppressor is used in an IC
remove the ions that cause background conductivity except those are being analyzed
A: show the result of a suppressor. B: all the ions are conducted, they increased the conductivity of solution
6.6c. II. it impossible to analyze CO3 and HCO3 on an IC
Extra H+ produced at the anode adjusts the pH, also react with HCO3- in solution to produce CO2 gas which leaves the suppressor before the detector
6.7a. Analysis of Fe3+,
AA(colorimetry), ICP, ICP-MS
6.7a. Analysis of Cl-
Titration with AgNO3, ISE, IC
6.7a. Analysis of Mg2+,Ca2+
titration with EDTA, AA(flame), ICP, ICP-MS
6.7a. Analysis of SO42-
scattering, IC
6.7a. Analysis of Na+,K+
AA, ICP, ICP-MS
6.7c. Analysis of HCO3, CO3
P, M titration
6.7c. Analysis of Co, Ni, Sn
ICP
6.7c. Analysis of NO2
AA, IC
6.1a. Contaminants ass w TDS
Anion: HCO3, silicate, chloride, sulfate, sulfide
Cation: K, Ca, Na, Sr, Ba
6.2a. TDS conductivity meter
A sample has its conductivity measured and the value obtained is compared to the conductivity of a standard made up of NaCl.
6.2b. Adv and Disad of a conductivity meter
Adv: cheap, easy to use, an analysis is quick
DIs: values are approximate
12.2 # kinds of interactions btw radiant E and materials or solution
absorption
emission
excitation
relaxation
- Wavelength range is characteristic of
a. visible radiation
b. ultraviolet radiation
c. infrared radiation
d. the highest radiation E
e. the lowest radiation E
- Wavelength range is characteristic of
a. 400-700nm
b. 1-130nm
c. 700-10^6
d. 10^12 nm
e. 10^-4 nm
12.6. # changes when absorbing ultraviolet in compare to infrared
UV or VIS causes electronic excitations
IR: vibration of molecules
6.3c. Describe absorption and emission using sketch
absorption: light source -> sample analyzed -> detector
emission: sample analyzed -> detector
11.28.
see Quiz
11.28.
see Quiz
6.3f. select a suitable wavelength for the detector
choose the wavelength at max absorbance
12.5 the basic components of instruments designed to measure absorption of radiant E
energy source ->energy spreader -> sample-> energy detector
12.12 Adv of ICP for metal analysis
- large linear range & low detection limits
- very few interferences
- can detect elements that resist thermal decomposition at the low temps of the flame used in AA
- can obtain many elements in an analysis
6.4b. Spectrophotometer are conventional or diode array
conventional-> built upon the same principles used in atomic emission spectrometry
samples are decomposed to neutral elements then to ions in high temps plasma and analyzed based on their mass to charges ratio
