QUANT

Ammonium Persulfate- Manganese in Iron
Steel has carbon in it therefore it us used to oxidize the carbon to make CO2. Takes Carbon out of steel sample
Ascorbic Acid- Manganese In Steel

Is a mild reducing agent  and is used to keep the manganese in the +2 oxidation state and also is a complexing agent. Complexes Manganese.

Potassium Periodate- Manganese in Steel
Osidizes manganese ion to the MnO4-. The MnO4- ion is colored (purple)
EDTA- Manganese in Steel
Standardized use to calculate the molarity of Manganese in manganese nitrate solution.

pH 10 buffer- Manganese in Steel

We want the experiment at a pH of 10 so EDTA can react (partially ionized), raises the pH to 10

Calgamite- Manganese in Steel
Is a colored indicator when titrating, turns from Red to Blue and purple indicates an almost end point.
Nitric Acid – Manganese in Steel
Dissolves the steel sample
Phosphoric Acid- Manganese in Steel
binds up Fe3+ (Iron) so i t wont be used in the reaction with Manganese. So it’s not available for oxidation.
As the ionic strength (;) increases…
the activity, ;, decreases
As the effective diameter, ;, decreases..
the activity, ;, becomes more important.
Solving Complicated Equilibria, Using systematic Treatment

1.) Write equilibrium reaction and their expression

2.) write a charge balance equation

3.) write a mass balance equation–> can’t be cretaed or destroyed.

Charge balance equation
where all the positive charges equal the negative ones.
Steps to Solving Complidated Equilibria

1.) Write reactions and K expressions

2.) write chareg balance

3.) write mass balance

4.) count equations and unknowns

5.) solve for unknowns- assumptions conditions

Ionic Strength
is a measure of the total concentration of ions in solution
EDTA ( Ethylenediuminetetraacetic Acid)

– Forms Comlex ions,

Metals = electron acceptor

EDTA+ electron donor from electrons on Oxygens

– pH Dependent ~ 10

 

Formation/ Stability Constant
the equilibrium constant for the reaction of a metal with a ligans (Kf)
Endpoint Monitor for EDTA
colorimetric indictaor (complexometric indicator)–> where the indicator actually binds to the metal
3 color indicators used with EDTA:

1.) Calmagite

2.) Eriochrome Black T

3.) Hydrosynapthol Blue

Calmagite

Doesn’t work for all metals just for: Zn 2+, Mn 2+, Mg 2+, Ca 2+

Red–> Blue

Eriochrome Black T

Used in limestone Ca 2+ and Mg 2+

Red–> Blue   Mg 2+

Hydroxynapthol Blue

Used at high pH and binds to Ca 2+

Red–> Blue

Types of Titrations

-Direct

– Indirect

Types of Indirect Titrations

– Back

– Displacement

Direct
Where the analyte reacts with EDTA if it’s at the right pH ( Zn2+, Mn 2+, cA 2+, Mg 2+)
Back Titration
Where you react metal (analyte) with excess EDTA in the flask. Put mpre EDTA in than what was needed. Titrate EDTA that is left with a standard metal solution (Zn 2+)
When is a Back Titration used?

– slow rxn

– not a good indicator

-analyte ppts. w/o EDTA w/ OH-

Displacement
where the analyte reacts with [Mg EDTA] complex, titrate mg 2+ with EDTA

When is displacement used?

 

– when the idicator is bad
2 types of Interference when titrating with EDTA:

1.) When there is another metal present abd both react w/ EDTA therefore do soemthing so only one is present.

2.) Metal binds tightly to indicator–> "metal blocks the indicator"

Metals that block Eriochrome Black T:

FE 3+, Al 3 +, Cr 3+, Co 2+, Ni 2+

How is blocking of Eriochorm Back T removed?
Masking- mask interference by making other metal bound to something else.
When masking for Fe 2+ what is used?
Cyanide, 6CN- (poison)
When masking for Al 3+ what is used?
2N(C2H4OH)2- triethenolamine
Transmittance (T)
The fraction of the original light that passes through the sample. = P/Po
Absorbance
The percent transmittance – log(Po/P)–> -log T

Pathway of measuring the Light Theory

Absorbtion (UV or VIS)–> wavelength selector–> Sample–>Detector–> Readout

Phosphorescence

emissions of light transmitted from triplet state to ground state
Flouresence
emissions of light transmitted from S1 to ground state. (shorter time to reach ground)
Factors that influence Absorbance

1.) Temperature

2.) pH of solution

3.) Solvent system

4.) Electrolyte concentration

Ways in which light can deviate from Beer’s Law and their corrections:

– Too concentrated of solution  Correction–> dilute sample

– Chemiscal Reaction  Correction–> Choose one w/o chem. rxns

– Instrumental- stray light  Correction–> use middle region or wavelength are

Absorbtion of light source with UV light in a Nova Spec instrument
Duterium (D2) lamp
Absorbtion of light with VIS light in a Nova Spec instrument
Tungston (W) filament
Two types of instruments for Spectroscopy

Singal Beam –> 1 pathway of light

1.) Novaspec

2.) Photodiode Array Instrument

Monochromater
dispereses light with a grating, in Novaspec
Novaspec detector
photomultiplier Tube
Photodiode Array Instrument
wavelength selector is polychromoater- can collect multiple wavelength of light and takes 5 seconds but has not as good of resolution
Types of Error in reading Absorbance:

– Bubbles in sample reflects and scatters light

-Inconsistant Sample placement, if not b (pathlength) changes

– Fingerprints/ other residue

– Not zeroing, baseline drift

-Light interferance

– Using and incorrect wavelength

-Drift

-Nonhomogenous sample

– Incorrect blank- matrix

– Interferences from other chemical species

Ferrous Ammonium Sulfate 6 hydrate in Limestone
Primary standard for standard solutions, did not dry for Fe 3+ determination in limestone analysis.
EDTA in Limestone
titrant for MgO and CaO was standardized
Erio-T indicator in Limestone
an alternative for calmagite for titrations of CaO and MgO
Hydroxynapthol Blue in Limestone
for Calcium titration, because calcium is done at the higher pH.
Potassium Cyanide in Limestone
Prevents interference to bond to iron and takes it out of the equation for EDTA.
pH 10 buffer in Limestone
Raises pH when titrating for CaO and MgO with calmagite.
Buffer
resists changes in pH when acids of bases are added or when dilution occurs
Ways to prepare a Buffer:

– Add a weak acid and it’s conjugate base to eachother

– start with a weak acid and add a strong base HA will make A-, HA> OH-

-Start with a weak base and add a strong acid and A- will make HA, A-> H3O+

Amphiprotic
can gain H+ or loose H+
3 M Sulfuric Acid- Limestone
 used to dissolve primary ammonium sulfate standard
Calmagite- Limestone
Used to titrate MgO and CaO as and indicator at lower pH.
12M HCL acid- Limestone

Used to disslove the limestone sample.

Hyrdoxylamine hydrochloride 10%- Limestone
Used to convert Fe3+ to Fe 2+ and reduce Copper to Copper I and also prevents the indicator from being oxidized. Fe 3+ absorbs at a different wavelength than Fe2+
1,10 Phenanthroline 1 %- Limestone
Binds with Fe 2+ and forms the bright orange color
Sodium Acetitate 1 M- Limestone
Used to form a buffer around pH 4 or 5 therefore Iron- phenanthroline can form best around
Triethanolamine- Limstone
Used to make a complex of mask the aluminum in solution before titrating
6 M KOH- Limestone
Adjust the pH to 12 to ppt the Mg so you can titrate Ca alone
Oxidation
Lose of Electrons
Reduction
Gain of electrons
Ways in which Redox reactions can be measured:

1.) Electric Charge (q=nxF)

2.) Eelctric Current (I = C/ sec= nF/sec)

3.) Eelectric Potential (E=work (J)/ q(C))

Types of Referance Electrodes:

-Standard Hydrogen electrode- composed of pH wire and H2(g) 1 bar and 1 MHCL

-Saturated Calomel Electrode- (SCE) Uses Hg2 Cl2(S) +electrons

– Silver/ Silver Chloride- Uses AgCl(s) and electrons

Types of Working Electrodes:

Metallic- Pt, Au

Membrane- pH and glass

2 types of Electrochemcial Cell

-Produce Electricity

– Use Electricity

When a electrochemical cell produces electricty?

Galvametric Cell ( Spontaneous , E is positive)–> camera and a phone

 

Whena Electrochimical cell uses electricity?
Electrolytic cell ( non spontaneous, e is negative)
Galvanic
when a electrochemical cell creats a voltage

Microwave

Rotation
Infrared
Stretching
UV and Light
Electronic excitation
X-rays
bond breaking and ionizing
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