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EVT: ENVS 359 QUIZ 3 > quiz 3 > Flashcards

quiz 3 Flashcards

1
Q

what are three methods to obtain TDS?

A
  1. Evaporation/weighing
  2. Conductivity
  3. Ion Analysis
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2
Q

Methods to obtain TDS (explain, +/-) : evaporation/weighing

A
  • Place known volume of sample in pre-weighed container -> in oven at 105*C -> dry until constant weight achieved
  • Calculate mg/L TDS: (final weight - initial)/initial

+/-
+ cheap: standard lab equipment and man power
+ time saving: obtain values in a few hours
- volatile substances change form when heated, can confuse TDS with DO

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3
Q

Methods to obtain TDS (explain, +/-) : Conductivity

A
  • measure sample conductivity -> compare to NaCl standard -> report TDS as sample made up of NaCl

+/-
+ conductivity meters are cheap and easy to use
- values are approximate

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4
Q

Methods to obtain TDS (explain, +/-) : Ion analysis

A
  • analyze individual ions ($$$ICP to $ISE) -> each ion mg/L -> sum of all ions is TDS mg/L

+/-
+ thorough and very accurate
- time consuming and expensive

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5
Q

Ways to obtain ion concentrations relevant to TDS (5)

A
  1. titrations
  2. IC - ion chromatography
  3. AA - atomic absorption
  4. ICP - atomic emission
  5. ISE - potentiometric analysis
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6
Q

Obtain [ion] relevant to TDS (explain + example) : titrations

A

What.

  • A solution of known concentration is reacted with a solution of unknown concentration to an end point.
  • Since reaction is stoichiometric, titration information is used to determine unknown concentration.

Examples.

  • acid/base - p and m
  • redox - residual chlorine
  • precipitation - chloride
  • complex formation - EDTA
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7
Q

Obtain [ion] relevant to TDS (explain + example) : IC

A

What.

  • Use of an ion exchange column to analyze for anions, usually involve conductivity detector.
  • Can be used for all anions except for HCO3- and CO32-

Examples.
Cl-, SO42-

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8
Q

Obtain [ion] relevant to TDS (explain + example) : AA

A

What.

  • Light is directed through a sample and the attenuation of the intensity is used to determine unknown concentration after a calibration curve has been obtained.
  • One unknown at a time
  • Unknown must have a suitable lamp

Examples.
Na+, Ca2+, Zn, Cu

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9
Q

Obtain [ion] relevant to TDS (explain + example) : ICP

A

What.

  • atomic emission
  • sample causes light -> wavelength and intensity used to determine unknown identity and concentration after a calibration curve has been obtained.

Examples.
Most cations, just not NH4+

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10
Q

Obtain [ion] relevant to TDS (explain + example) : ISE

A

What.

  • potentiometric analysis
  • electrode is designed that measures the activity (ie. concentration) of a particular ion via a reaction at an anode or cathode
  • potential relative to reference electrode on calibration curve to obtain unknown concentration

Examples
chloride, ammonium

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11
Q

Equation for frequency

A

v = c/wavelength

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12
Q

photon energy equation

A

E = hv

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13
Q

Describe how molecules absorb different wavelengths (4)

A
  1. microwave: molecule rotates
  2. IR: molecules vibrate
  3. VIS: electronic excitation
  4. gamma: inner shell electrons excited
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14
Q

What is T

A

Transmittance

measurement of light that has passed through the sample

= I/Io

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15
Q

What is T%

A

T x 100

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16
Q

equation for absorbance

A

A = 2-log10%T

17
Q

Schematics for the different spec analysis (3)

A
  1. absorption
    light -> sample -> detector
  2. emission
    sample -> detector
  3. scattering

light -> sample ->
|
v
detector

18
Q

analyte

A

components of a sample that are being determined

19
Q

blank solution (def and use)

A

solution containing all analysis reagents and solvents, but no analyte.

takes into parameters of analysis that are being affected by outside factors that are not analyte -> equipment, matrix

20
Q

standard solution (def and use)

A

concentration of solute known with high reliability

used to plot calibration curve and solve for concentration of analyte in unknown

21
Q

advantages of ICP (4)

A
  1. obtain many elements in one analysis
  2. large linear range and low detection limit
  3. very few interferences
  4. can detect elements that resist decomposition during FAA
22
Q

What is linear range

A

Range of values where output signal is a direct, linear function of input signal - line of best fit follows a straight line

23
Q

detection limit

A

when a reading is below this limit -> absorbance signal is less than background noise

24
Q

intrapolation and extrapolation

A

Both involve drawing line of best fit to obtain non-measured values.

  • intrapolation: line between highest and lowest data points
  • extrapolation: line extends past highest and lowest data points
25
Q

In IC, ______ are separated by ____ _________ and are detected by _______.

A

In IC, anions are separated ion exchange and are detected by conductivity.

26
Q

Point of supressor

A

Solution has high conductivity -> which is a high background signal. Suppressor removes all ions except those being analyzed.

27
Q

Why can’t analyze for HCO3-, CO32- in IC

A

Suppressor removes background signal, they are the easiest anions to eliminate -> adjust pH and they are removed as CO2 (g)

28
Q

2 Ways to analyze for each Fe3+, Cl-, Mg+, SO42-, Na+

A 
Fe: colorimetry, FAA, ICP, ICP MS
Cl: ISE, IC, silver nitrate titration
Mg: EDTA titration, FAA, ICP, ICP MS
SO4: scattering, IC
Na: AA, ICP, ICP MS
29
Q

Way to analyze each CO32-, HCO3-, Co+, Ni+, Sn+, NO2

A 
CO3: p and m titration
HCO: p and m titration
Co: ICP
Ni: ICP
Sn: ICP
NO2: IC
30
Q

analytical technique used for anions, plus exception

A

IC, exception is HCO3 and CO3

31
Q

analytical technique used for cations, plus exception

A

ICP, exception is NH4

32
Q

Approaches to deal with water that is at risk for scaling (4)

A
  1. Allow scale to build up and then manage
    Ex., Carbonate with acetic acid, silica with hydroflouric acid
  2. Chemicals to prevent scale - when added they dissolve scale
    Ex., Crystal modifier, chelating agent
  3. Remove ions before they precipitate
    Ex., LS (LS, WLS, HLS), IX, NF
  4. Reverse water -> remove solids
    Ex., Get water (RO, evaporators), Get solid (boiler, cooling tower)
33
Q

Difference between TDS and TSS

A

TDS - dissolved inorganic salts

TSS - precipitate

34
Q

Cold lime softening

A

Softening completed at ambient temps to remove TDS as precipitate

Ca(HCO3)2 (aq) + Ca(OH)2 (aq) -> 2CaCO3 (s) + 2 H20 (l) + Energy

35
Q

How to remove permanent hardness (CaCl2)

A

Remove using soda ash (Na2CO3) and sodium aluminate (Na2Al2O4) to increase pH

36
Q

Consideration needed when using slaked lime (Ca(OH)2)

A

Only use exact amount needed, otherwise contributing what want to remove

37
Q

Warm lime softening

A

T: 120 - 140 F

+: recover waste heat and convert to energy, decrease $ by reducing load on demineralizer, lower blowdown discharge for cooling systems

38
Q

Hot lime softening

A

T: 227 - 240 F

EVT: ENVS 359 QUIZ 3 (1 decks)

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