Final Exam

Rover Curiosity include:

Mineral Identification camera.

Chemical composition spectrometer.

Weather sensors.

Rock-vaporising laser and chemical identification camera.

Organic compound detector. 

Radiation Sensor

Hydrated mineral sensor.

EPA Lowering of arsenic levels.
From 50 to 10 ug/L
Taurine
Found in chocolate; Organic acid widely distributed in animal tissue. Major constituent of bile; can be found in large intestines. Function for conjugation of bile acids and antioxidizing.

Safety Label

Top

Left

Right

Bottom

Top(red) Fire hazard 0-4

Left (Blue): Health 0-4

Right(Yellow): Reactivity 0-4

Bottom(White): Info

graduated readings
Estimate to nearest 10th of division. I.g. 0.10ml divisions can be read 0.11ml.
Tolerances of class A burets.
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Tolerance class A volumetric flask.
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1.Precision

2.Accuracy

3.Systematic Error

4.Random Error

1. Reproducibility; how close the measurements are to each other.

2. How close the measurements are to real values.

3. Determinate error; values are either all high or all low.

4. Indeterminate error. 

T-test

Case 1: Compare an answer with accepted value

Case 3: Testing two methods (paired t-test).

Can also be used to determine if one datum is out of the norm.

Most common estimates of uncertainty

1. Confidence interval

2. Standard deviation

Q-test

Aka Grubbs’test. Determine if one datum point should be rejected.

Gap/Range

if Q is greater, than table, value can be rejected. 

Least Square
Means to evaluate calibration curves.
Calibration curves error of y vs x
y value errors are greater than x value errors.
Single blind studies
Use samples identified the lab as performance evaluation studies.
Double blind studies
Use standards, but the measurer doesn’t know that.
Control chart
Visual representation of confidence intervals for a Gaussian distribution. Warns observer whether values stray dangerously from the standard.
Observation on a control chart that requires troubleshooting.

1 observation beyond the action lines

2 to 3 consecutive measurements between warning and action lines.

6 consecutive all increasing or all decreasing measurements. 

7 consecutive measurements all above or all below the center line 

14 consecutive points alterning up and down

An obvious nonrandom pattern

Quality assurance process

Use objectives

Specifications

Assessment

Method validation
Methods proving that a process is valid.
Specificity
How good he instrument is at seperating the intended analyte from other stuff.
Linearity
How well the curves follow a straight line.
How to determine accuracy

1. Compare with ceritified reference

2. Compare results from one or two analytical methods.

3. Analyze blank sample spiked with known analyte.

4. Standard addition

 

How to determine precsion

Instrument precision(repetitive injections)

Intra-assays: Same person, smae method

Ruggedness: different people, day, instruments

Inter-laboratory: the greatest

 

Range
Concentration over which reliable data can be obtained.
Detection limit
Smallest quantity of analyte that is significantly different. 3s/m
What does the slope of a calibration graph tells us?
Method sensitivity.
Minimum limit of detection Lower limit of quantification
3s/m 10s/m
What does the method of standard addition require?
Linear response to analyte.
Standard addition and internal standard

Standard: Known quantity of analyte is added

Internal: Known quantity of non analyte is added.

When are internal standards useful?
When quantity of sample analyzed or instrument reponse varies from time to time because of uncontrollable conditions.
Signs of S, H, G and K when a reaction is favored.

S>0

H<0

G<0

K>1

Common Ion effect
Salt is less solubl when constituent ions are already in mixture.
Through what atom does water bind to cationS??
Oxygen
Which ions bind to molecules more tightly?
Smaller more highly charged.
What is ionic strength? How is ionic strength increased?
Total concentration of ions in solution. Inert salt is added.
As ka increases
pKa decrease; acid strength decreases
End point on a titration curve

Volume where slope is greatest

Maximum of first derivative

The inflection point of the second derivative

What is a current

The quantity of charge flowing each second through a circuit.

1A = 1C/S

Relationship between charge and mole.

Work and voltage.

Free energy and electric potential.

Ohms law

Electric power

q=nF

Work= Eq

deltaG=-nFE

I= E/R

P= Work/S=EI

Oxidation electrode

Reduction electrode

Anode

Cathode

What does a galvanic cell use to generate electricity?
Spontaneous reaction.
What SHE? and what is it used for?
It is the standard hydrogen electrode. Consist of a catalytic Pt surface, and an acidic solution. Used to deduce the standard electric potential of other cells.
Refrence electrode.
Maintains a fixed potential.
Junction potential and causes it?
Voltage difference formed when two dissimilar electrolyte solutions are in contact. Greater mobility of one ion compared to the other. The potential will slow down Cl- and accelerate Ag+.
What does the difference accross a membrane depend on?
Activity of analyte in outer solution.
Most common ion-selective electrode
Glass electrode
Categories of ion-selective electrodes.

Glass membranes: for H+ and certain monovalent cations
Solid-state electrodes: based on inorganic crystals or, recently, conductive polymers
Liquid-based electrodes: using a hydrophobic polymer membrane saturated with a hydrophobic liquid ion exchanger
Compound electrodes: with an analyte
selective electrode enclosed by a membrane that separates analyte from other species or that generates analyte in a chemical reaction.

Advantages and disadvantages of ion-selective electrodes:

A:

Respond linearly to logarithm of analyte over 6 order of magnitude

Do not consume unknowns; negligible contamination

Fast response time

Color and turbity do not hinder them

D:

Low precision

Can be cloaged

Fragile and limited shelf life

Only measure free analytes

Potentiometry vs electrolysis

1. measures voltage in absence of current.

2. Forces current to make reaction happen.

Constant current vs controlled potential coulometry
Constant current is linear controlled potential is exponential.
What part of the molecule is responsible for light absorption?
Chromophore.
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