Lectures 1-4 Flashcards Preview

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Flashcards in Lectures 1-4 Deck (22):
1

What is the difference between quantitative and qualitative analysis?

Qualitative tells you what is present
Quantitative tells you how much is present

2

What is an absolute or classical method of analysis?

Eg gravimetric or titrinetric.
In titimetric the amount of analyte is measured by the volume of reagent solution added to completely react with it.
In gravimetric analysis the amount of analyte is measured by the weight of the product produced

Using known concentration is a must - stoichiometry

3

What is a standard or empirical technique?

One that required standards to be known and the amount of analyte can only be figured using a standard curve eg.
Also usually require an instrument (spectrometer, chromatograph)
Use of calibration

4

For quantitative analysis what are the 5 steps?

Sampling
Storage
Pre treatment
Determination
Treatment of results

5

Why is sampling so important?

The sample must be representative or the analysis will be incorrect

6

Give examples of conditions that need to be controlled during storage of a sample?

Temperature
pH
Type of container
Pressure
O2
Etc

7

What steps of pre treatment can be carried out? And why?

To make the sample suitable for analysis it may be
Insoluble samples dissolved or digested with acid due to most samples being aqueous
Extraction
Derivatisation
Filtration
Centrifugation

Pretreatment is also important to remove the analyte from the MATRIX(everything else in the sample other than the analyte)
The matrix can interfere and prevent accurate determination of the analyte

8

What is the difference between a physical and chemical interference?

A physical will physically interfere eg making sample to viscous

A chemical interference will react with the analyte of another component to prevent successful analysis

9

What is the determination step of analysis?

Standards containing known amounts of analyte prepared and using calibration curves the amount of analyte in unknown solution is measured

10

What is Treatment of results?

The conversation of the measured concentration back to actual amount in original sample validity is measured using accuracy and precision measurements

11

What is the meaning of accuracy and precision?

Accuracy is how close you are to expected values
Precision is how close all your values are to each other

12

What is the equation for measuring accuracy(E)?

E=Xi -Xt

Where Xi is the measured value
Where Xt is the true or expected value

13

What is the equation used to measure precision(variance)?

Standard deviation
Learn standard deviation equation

Sum of ((Xi -Xbar)squared)/N-1 all square rooted

N is number of measurements
Xbar is average result
Xi is measured value

14

What is he difference between different forms of electromagnetic radiation?

It’s wavelength and relation properties

15

What comments can be made about the energy types of radiation carries and it’s wavelengths?

Wavelength is proportional to the energy it carries.
Shorter wavelengths having more energy and and longer wavelengths having less energy

16

What is radiation compared to?

A steam of photons

17

Order the wavelengths of the 7 types of radiation?

Radio frequency 1-100m
Microwaves 10^-2m - 10^-1m
Infrared 10^-5m
UV/Visible 10^-6m - 10^-7m
Vacuum UV 10^-8m - 10^-9m
X-rays 10^-10m - 10^-11m
Gamma rays - 10^-12m >

18

What are the two equations used for energy of a photon and what is derived from them?

E=hv
c=ŷv
E=energy of photon
v=frequency of radiation
Ŷ=wavelength
c=velocity of light

E=hc/ŷ

19

Where is the UV/Visible Region?

Between 200nm and 800nm
UV A between 320-400nm
UV B between 280-320nm
UV C between 200-280

20

What is spectroscopy seen as?

The interaction of electromagnetic radiation with matter.
The radiation is stored by atoms and molecules then released, this is usually viewed as the absorption of photons of radiation by atoms or molecules

21

What are the four main stores of energy that molecules employ?

Electronic (UV/Vis)
Vibrational (IR)
Rotational (Microwave)
Translational

Etotal = elec +vib+rot+trans
Absorbing the right phon allows the molecule to jump the energy gap

22

Explain Eelec, Evib, Erot and E trans and their region on the ectromagnetic spectrum?

Eelec - correspond to energy of orbital occupied by the electron. Movement of valence electrons to unoccupied orbitals at energy equivalent to UV/Vis photons
Evib - correspond to vibrational state of molecule. Translation requires energy equivalent to IR photons
Erot - correspond to the rotational state of the molecule. Faster rotational state requires energies equivalent to microwave photon.
Etrans - corresponds to motion of molecule through space. Translation from one velocity to another. Almost neglible movement due to space being so small but continuous.